Topic outline

  • UNIT 1: ARITHMETICS

    Key Unit competence: Use arithmetic operations to solve simple real life problems

    1.O. Introductory Activity
    The simple interest earned on an investment is I prt = where I is the
    interest earned, p is the principal, r, is the interest rate and t is the time in
    years. Assume that 50,000Frw is invested at annual interest rate of 8%
    and that the interest is added to the principal at the end of each year.
    a. Discuss the amount of interest that will be earned each year for 5
    years.
    b. How can you find the total amount of money earned at the end of
    these 5 years? Classify and explain all Mathematics operations
    that can be used to find that money.

    1.1 Fractions and related problems
    Activity 1.1
    1) Sam had 120 teddy bears in his toy store. He sold 2/3 of them at 12
    Rwandan francs each. How much did he receive?
    2) Simplify the following fractions and explain the method used to simplify.

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    3) Given that the denominator is different from zero,

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    4) Do you some times use fractions in your life? Explain your answer.

    CONTENT SUMMARY
    Consider the expressions OK in each of these, the numerator or
    the denominator or both contain a variable or variables. These are examples
    of algebraic fractions. Since the letter used in these fractions stand, for real
    numbers, we deal with algebraic fractions in the same way as we do with
    fractions in arithmetic. Fractions can be simplified and operations on fractions
    such as addition, subtraction, multiplication and division can be applied in
    simple arithmetic for solving related problems.

    Adding fractions:
    To add fractions there is a simple rule ok

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    Dividing fractions
    To divide fractions, first flip the fraction we want to divide by, then use the
    same method as for multiplication

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    A method of calculating the interest rate on an investment is explained in the

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  • UNIT2 : EQUATIONS AND INEQUALITIES

    Key Unit competence: Model and solve daily life problems using 

                                                   linear, quadratic equations or inequalities

    2.O. Introductory Activity

    1) By the use of library and computer lab, do the research and explain 

    the linear equation. 

    2) If x is the number of pens for a learner, the teacher decides to give 

    him/her two more pens. What is the number of pens will have a learner 

    with one pen? 

    a) Complete the following table called table of value to indicate the numberokof pens for a learner who had x pens for x ≥ 0 .

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    CONTENT SUMMARY 

    An equation is a mathematical statement expressing the equality of two 

    quantities or expressions. Equations are used in every field that uses real 

    numbers. A linear equation is an equation of a straight line.

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    Real life problems involving linear equations

    Problems which are expressed in words are known as problems or applied 

    problems. A word or applied problem involving unknown number or quantity 

    can be translated into linear equation consisting of one unknown number 

    or quantity. The equation is formed by using conditions of the problem. By 

    solving the resulting equation, the unknown quantity can be found.

    In solving problem by using linear equation in one unknown the following 

    steps can be used:

    i) Read the statement of the word problems

    ii) Represent the unknown quantity by a variable

    iii) Use conditions given in the problem to form an equation in the 

    unknown variable

    iv) Verify if the value of the unknown variable satisfies the conditions of 

    the problem.

    Examples 

    1) The sum of two numbers is 80. The greater number exceeds the smaller 

    number by twice the smaller number. Find the numbers.

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    2.6 Solving algebraically and graphically simultaneous linear inequalities in two unknown

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    2.7 Solving quadratic equations by the use of factorization and discriminant

    Activity 2.7

    Smoke jumpers are fire fighters who parachute into areas near forest 

    fires. Jumpers are in free fall from the time they jump from a plane until 

    they open their parachutes. The function ok gives a jumper’s 

    height y in metre after t seconds for a jump from1600m. 

    a) How long is free fall if the parachute opens at1000m?

    b) Complete a table of values for t = 0, 1, 2, 3, 4, 5 and 6.

    CONTENT SUMMARY

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    CONTENT SUMMARY

     When only two or single variables and equations are involved, a simultaneous equation system can be related to familiar graphical solutions, such as supply and demand analysis.

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    2.9. END UNIT ASSESSMENT

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  • UNIT 3: DESCRIPTIVE STATISTICS

    3.0. Introductory Activity 

    1) 1. At the market a fruit-seller has the following daily sales Rwandan francs for five consecutive days: 1000Frw, 1200Frw, 125Frw, 1000Frw, and 1300Frw. Help her to determine the money she could get if the sales are equally distributed per day to get the same total amount of money.

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    2) During the welcome test of Mathematics for the first term 10 studentteachers of year one language education scored the following marks 

    out of 10 : 3, 5,6,3,8,7,8,4,8 and 6. 

    a) What is the mean mark of the class? 

    b) Chose the mark that was obtained by many students.

    c) Compare the differences between the mean of the group and the 

    mark for every student teacher.

    3.1 Definition and type of data

    Learning activities 3.1

    Carry out research on statistics to determine the meanings of statistics 

    and types of data. Use your findings to select qualitative and quantitative 

    data from this list: Male, female, tall, age, 20 sticks, 45 student-teachers, 

    and 20 meters, 4 pieces of chalk.

    CONTENT SUMMARY

    Statistics is the branch of mathematics that deals with data collection, data 

    organization, summarization, analysis and draws conclusions from data.

    The use of graphs, charts, and tables and the calculation of various 

    statistical measures to organize and summarize information is called 

    descriptive statistics. Descriptive statistics helps to reduce our information to 

    a manageable size and put it into focus. 

    Every day, we come across a wide variety of information in form of facts, 

    numerical figures or table groups. A variable is a characteristic or attribute 

    that can assume different values. Data are the values (measurements or 

    observations) that the variables can assume.

    Variables whose values are determined by chance are called random 

    variables. A collection of data values forms a data set. Each value in the 

    data set is called a data value or a datum. 

    For example information related to profit/ loss of the school, attendance 

    of students and tutors, used materials, school expenditure in term or year, 

    etc. These facts or figure which is numerical or otherwise, collected with 

    a definite purpose is called data. This is the word derived from Latin word 

    Datum which means pieces of information. 

    Qualitative variable

    The qualitative variables are variables that cannot be expressed using 

    a number. A qualitative data is determined when the description of the 

    characteristic of interest results is a non-numerical value. A qualitative 

    variable may be classified into two or more categories. Data obtained by 

    observing values of a qualitative variable are referred to as qualitative data.

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    The possible categories for qualitative variables are often coded for the 

    purpose of performing computerized statistical analysis so that we have 

    qualitative data. 

    Quantitative variable

    Quantitative variables are variables that are expressed in numerical terms, 

    counted or compared on a scale. A quantitative data is determined when the 

    description of the characteristic of interest results in numerical value. When 

    measurement is required to describe the characteristic of interest or when it 

    is necessary to perform a count to describe the characteristic, a quantitative 

    variable is defined. 

    Discrete data is a quantitative data whose values are countable. Discrete 

    data usually result from counting. 

    Continuous data is a quantitative data that can assume any numerical 

    value over an interval or over several intervals. Continuous data usually 

    results from making a measurement of some type. Data obtained by 

    observing values of a quantitative variable are referred to as quantitative 

    data. Quantitative data obtained from a discrete variable are also referred to 

    as discrete data and quantitative data obtained from a continuous variable 

    are called continuous data.

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    Data can be used in different ways. The body of knowledge called statistics 

    is sometimes divided into two main areas, depending on how data are used. 

    The two areas are descriptive statistics and inferential statistics.

    Descriptive statistics consists of the collection, organization, summarization, 

    and presentation of data.

    Inferential statistics consists of generalizing from samples to populations, 

    performing estimations and hypothesis tests, determining relationships 

    among variables, and making predictions.

    A population consists of all subjects (human or otherwise) that are being 

    studied.

    A sample is a group of subjects selected from a population.

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    3.2 Data presentation or organization 

    Activity 3.2

    1) At the beginning of the school year student-teachers came to school 

    with all requirements materials and others don’t attend the school on 

    first day. The table below shows the number of student-teachers who 

    attended the school in 5 classrooms on first day.

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    Present the above data on bar chart and discuss what you can say when interpreting the chart. 

     2) One tutor of TTC wants to check the level of how his/her student-teachers like different subjects taught in Language Education option. The survey is done on 60 student-teachers. Here is the number of participants of the survey.

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    CONTENT SUMMARY

    After the collection of data, the researcher needs to organize and present 

    them in order to help those who will benefit from the research and lead him 

    or her to the conclusion. When the data are in original form, they are called 

    raw data and are listed next. 

    Raw data

    After the collection of data, one can present them in the raw form presentation.

    Example

    The following are numbers of notebooks for 54 student-teachers.

    3 4 5 6 6 7 3 2 5 4 5 7 4 3 2 3 6 5

    8 5 6 4 2 6 5 3 4 7 9 8 6 7 4 5 4 6

    3 4 3 6 7 8 2 7 6 5 4 6 4 7 8 9 9 5

    Since little information can be obtained from looking at raw data, the 

    researcher organizes the data into what is called a frequency distribution. A 

    frequency distribution consists of the number of times each values appears 

    in the raw data and sometimes the corresponding percentage vis-à-vis the 

    total number in the sample.

    1. Frequency distribution 

    Data can be presented in various forms depending on the type of data 

    collected. A frequency distribution is the organization of raw data in the 

    table form by the use of frequencies. 

    Example 

    The following data represent marks obtained by 12 student-teachers out of 

    20 in mathematics test of a certain TTC.

    13 10 15 17 17 18

    17 17 11 10 17 10

    The set of outcomes is displayed in a frequency table, as illustrated below:

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    The total frequency is the number of items in the population. In the survey 

    about the marks of student-teachers above, the total frequency is the number 

    of all student-teachers. We find this by adding up the numbers from the third 

    column of the table: 2112 51 +++ + + which is equal to 12 .

    Grouped data 

    When the number of data is too large, a simple distribution is not appropriate. In this case we come up with a grouped frequency distribution. A grouped frequency distribution organizes data into groups or classes

    Definitions related to grouped frequency distribution 

    a) Class limits: The class limits are the lower and upper values of the class 

    b) Lower class limit: Lower class limit represents the smallest data value that can be included in the class. 

    c) Upper class limit: Upper class limit represents the largest data value that can be included in the class. 

    d) Class mark or class midpoint:

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    Example: 

    The following data represent the marks obtained by 40 students in 

    Mathematics test. Organize the data in the frequency table; grouping the 

    values into classes, stating from 41-50: 

    54 83 67 71 80 65 70 73 45 60 72 82 79 78 65 54 67 64 54 76 45 63 49 52

    60 70 81 67 45 58 v69 53 65 43 55 68 49 61 75 52.

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    The classes: 41-50, 51-60, 71-80, 81-90

    Lower class limits: 41, 51, 61, 71, and 81

    Upper class limits: 50, 60, 70, 80, and 90

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    Class boundaries 

    Class boundaries are the midpoints between the upper class limit of a class and the lower class limit of the next class. Therefore each class has a lower and an upper class boundary.

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    For [10,15[ the lower class boundary is 10, The upper class boundary is 15 Class width =−= 15 10 5 

    We have Categorical Frequency Distributions and Grouped Frequency Distributions.

    The categorical frequency distribution is used for data that can be placed in specific categories, such as nominal- or ordinal-level data. 

    Example: 

    Data such as political affiliation, religious affiliation, or major field of study would use categorical frequency distributions. 

     Example: 

     Twenty-five army inductees were given a blood test to determine their blood type.

    The data set is: 

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    Grouped Frequency Distributions

    When the range of the data is large, the data must be grouped into classes 

    that are more than one unit in width, in what is called a grouped frequency 

    distribution. For example, a distribution of the number of hours that boat 

    batteries lasted is the following:

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    The procedure for constructing a grouped frequency distribution, i.e., when 

    the classes contain more than one data value

    Example

    These data represent the record high temperatures in degrees Fahrenheit 

    (*F) for each of the 50 states. Construct a grouped frequency distribution for 

    the data using 7 classes.

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    1) Determine the classes 

    – Find the highest value and lowest value: H =134 and L=100. 

    – Find the range: R = highest value-lowest value H -L, so 

    R=134 -100 = 34

    – Select the number of classes desired (usually between 5 and 20). In this case, 7 is arbitrarily chosen. 

     – Find the class width by dividing the range by the number of classes

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    – Select a starting point for the lowest class limit. This can be the smallest 

    data value or any convenient number less than the smallest data value. 

    In this case, 100 is used. Add the width to the lowest score taken as the 

    starting point to get the lower limit of the next class. Keep adding until 

    there are 7 classes, as shown, 100, 105, 110, etc.

    – Subtract one unit from the lower limit of the second class to get the 

    upper limit of the first class. Then add the width to each upper limit to 

    get all the upper limits. 105-1=104.

    The first class is 100–104, the second class is 105–109, etc.

    – Find the class boundaries by subtracting 0.5 from each lower class 

    limit and adding 0.5 to each upper class limit:

    99.5–104.5, 104.5–109.5, etc.

    2) Tally the data

    3) Find the numerical frequencies from the tallies.

    The completed frequency distribution is

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    2. Cumulative frequency 

    The cumulative frequency corresponding to a particular value is the sum of all frequencies up to the last value including the first value. Cumulative frequency can also defined as the sum of all previous frequencies up to the current point.

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    4. Histograms, Frequency Polygons, and Ogives 

    After you have organized the data into a frequency distribution, you can present them in graphical form. The purpose of graphs in statistics is to convey the data to the viewers in pictorial form. It is easier for most people to comprehend the meaning of data presented graphically than data presented numerically in tables or frequency distributions. 

    The three most commonly used graphs in research are 

    1) The histogram. 

    2) The frequency polygon. 

    3) The cumulative frequency graph or ogive (pronounced o-jive). 

    a) The Histogram 

    The histogram is a graph that displays the data by using contiguous vertical bars (unless the frequency of a class is 0) of various heights to represent the frequencies of the classes. 

    Example: 

    Construct a histogram to represent the data shown for the record high temperatures for each of the 50 states.

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    Step 1: Draw and label the x and y axes. The x axis is always the horizontal  axis, and the y axis is always the vertical axis. 

    Step 2: Represent the frequency on the y axis and the class boundaries on the x axis.

    Step 3: Using the frequencies as the heights, draw vertical bars for each class. See Figure below

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    b)The Frequency Polygon

    The frequency polygon is a graph that displays the data by using lines that 

    connect points plotted for the frequencies at the midpoints of the classes. 

    The frequencies are represented by the heights of the points. 

    Example: 

    Using the frequency distribution given in Example 2–4, construct a frequency polygon

    Step 1 Find the midpoints of each class. Recall that midpoints are found by 

    adding the upper and lower boundaries and dividing by 2:

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    Step 2 Draw the x and y axes. Label the x axis with the midpoint of each class, and then use a suitable scale on the y axis for the frequencies.

    Step 3 Using the midpoints for the x values and the frequencies as the y values, plot the points.

    Step 4 Connect adjacent points with line segments. Draw a line back to the x axis at the beginning and end of the graph, at the same distance that the previous and next midpoints would be located, as shown in Figure 2–3.

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    The frequency polygon and the histogram are two different ways to represent 

    the same data set. The choice of which one to use is left to the discretion of 

    the researcher.

    c) The Ogive

    The ogive is a graph that represents the cumulative frequencies for the 

    classes in a frequency distribution.

    Step 1: Find the cumulative frequency for each class.

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    Step 2: Draw the x and y axes. Label the x axis with the class boundaries. Use an appropriate scale for the y axis to represent the cumulative frequencies.

    (Depending on the numbers in the cumulative frequency columns, scales such as 0, 1, 2, 3, . . . , or 5, 10, 15, 20, . . . , or 1000, 2000, 3000, . . . can be used.

    Do not label the y axis with the numbers in the cumulative frequency column.) 

    In this example, a scale of 0, 5, 10, 15, . . . will be used.

    Step 3 Plot the cumulative frequency at each upper class boundary, as shown in Figure below. Upper boundaries are used since the cumulative frequencies represent the number of data values accumulated up to the upper boundary of each class.

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    Step 4 Starting with the first upper class boundary, 104.5, connect adjacent points with line segments, as shown in the figure. Then extend the graph to the first lower class boundary, 99.5, on the x axis.

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    Cumulative frequency graphs are used to visually represent how many values are below a certain upper class boundary. For example, to find out how many record high temperatures are less than 114.5_F, locate 114.5_F on the x axis, draw a vertical line up until it intersects the graph, and then draw a horizontal line at that point to the y axis. The y axis value is 28, as shown in the figure.

    5. Relative Frequency Graphs

    The histogram, the frequency polygon, and the ogive shown previously were constructed by using frequencies in terms of the raw data. These distributions can be converted to distributions using proportions instead of raw data as frequencies. These types of graphs are called relative frequency graphs.


    Example:

    Construct a histogram, frequency polygon, and ogive using relative frequencies for the distribution (shown here) of the kilometers that 20 randomly selected runners ran during a given week.

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    Solution:

    Step 1: Convert each frequency to a proportion or relative frequency by dividing the frequency for each class by the total number of observations.

    Place these values in the column labeled Relative frequency.

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    Step 2: Find the cumulative relative frequencies. To do this, add the frequency in each class to the total frequency of the preceding class. In this case, 0 +0.05 = 0.05, 0.05 + 0.10 = 0.15, 0.15 +0.15 =0.30,

    0.30+0.25=0.55, etc. Place these values in the column labeled Cumulative relative frequency.

    An alternative method would be to find the cumulative frequencies and then convert each one to a relative frequency.

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    Step 3: Draw each graph as shown in Figure 2–7. For the histogram and ogive, use the class boundaries along the x axis. For the frequency polygon, use the midpoints on the x axis. The scale on the y axis uses proportions.

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    6. Pie chart 

    A pie chart is used to display a set of categorical data. It is a circle that is divided into sections or wedges according to the percentage of frequencies in each category of the distribution.

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    Since there are 0 360 in a circle, the frequency for each class must be converted into a proportional part of the circle. This conversion is done by using the formula.

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    where f is frequency for each class and n is the sum of the frequencies. 

    Hence, the following conversions are obtained. The degrees should sum to 

    360. 

    Each frequency must also be converted to a percentage by using the formula

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    Next, using a protractor and a compass, draw the graph using the appropriate 

    degree measures found in step 1, and label each section with the name and 

    percentages.

    Example:

    1) One tutor in TTC want to check the level of how his/her student and teachers like different subject taught in Language Education option. The survey done on 60 student-teachers in English, Mathematics, French, Entrepreneurship and Kinyarwanda.

    Here is the results he/she obtained respectively after making survey 12, 24, 6, 10, and 8. Present the data on pie chart.

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    2) Construct a pie graph showing the blood types of the army inductees described above. The frequency distribution is repeated here.

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    Solution:

    Step 1: Find the number of degrees for each class, using the formula.

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    Step 3: Using a protractor, graph each section and write its name and corresponding percentage, as shown in the Figure

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    7. Stem and Leaf Plots

    The stem and leaf plot is a method of organizing data and is a combination 

    of sorting and graphing. It uses part of the data value as the stem and part 

    of the data value as the leaf to form groups or classes. It has the advantage 

    over a grouped frequency distribution of retaining the actual data while 

    showing them in graphical form.

    Examples: 

    1) At an outpatient testing center, the number of cardiograms performed 

    each day for 20 days is shown. Construct a stem and leaf plot for the data.

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    Step 1: Arrange the data in order: 02, 13, 14, 20, 23, 25, 31, 32, 32, 32, 

    32, 33, 36, 43, 44, 44, 45, 51, 52, 57

    Note: Arranging the data in order is not essential and can be cumbersome 

    when the data set is large; however, it is helpful in constructing a stem 

    and leaf plot. The leaves in the final stem and leaf plot should be arranged 

    in order.

    Step 2 Separate the data according to the first digit, as shown. 

    02 13, 14 20, 23, 25 31, 32, 32, 32, 32, 33, 36, 43, 44, 44, 45 51, 52, 57

    Step 3: A display can be made by using the leading digit as the stem and 

    the trailing digit as the leaf. 

    For example, for the value 32, the leading digit, 3, is the stem and the 

    trailing digit, 2, is the leaf. For the value 14, the 1 is the stem and the 4 is 

    the leaf. Now a plot can be constructed as follows:

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    It shows that the distribution peaks in the center and that there are no 

    gaps in the data. For 7 of the 20 days, the number of patients receiving 

    cardiograms was between 31 and 36. The plot also shows that the testing 

    center treated from a minimum of 2 patients to a maximum of 57 patients 

    in any one day.

    If there are no data values in a class, you should write the stem number 

    and leave the leaf row blank. Do not put a zero in the leaf row.

    2) The mathematical competence scores of 10 student-teachers participating 

    in mathematics competition are as follows: 15, 16, 21, 23, 23, 26, 26, 30, 

    32, 41. Construct a stem and leaf display for these data by using 2, 3, 

    and 4 as your stems.

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    3) The following are results obtained by student-teachers in French out of 

    50. 

    37, 33, 33, 32, 29, 28, 28, 23, 22, 22, 22, 21, 21, 21, 20, 

    20, 19, 19, 18, 18, 18, 18, 16, 15, 14, 14, 14, 12, 12, 9, 6

    Use stem and leaf to display data

    Solution: 

    Numbers 3, 2, 1, and 0, arranged as a stems to the left of the bars. The 

    other numbers come in the leaf part.

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    Application activity 3.2 

    1) Suppose that a tutor conducted a test for student-teachers and the 

    marks out of 10 were as follows: 3 3 3 5 6 4 6 7 8 3 8 8 8 10 9 

    10 9 10 8 10 6

    a) Draw a frequency table;

    b) Draw a relative frequency table and calculate percentage for each;

    c) Present data in cumulative frequency table, hence show the 

    number of student-teachers who did the test.

    2) During the examination of English, student-teachers got the following 

    results out of 80: 54, 42, 61, 47, 24, 43, 55, 62, 30, 27, 28, 43, 54, 46, 

    25, 32, 49, 73, 50, 45. 

     Present the results using stem and leaf.

    3) A firm making artificial sand sold its products in four cities: 5% was 

    sold in Huye, 15% in Musanze, 15% in Kayonza and 65% was sold 

    in Rwamagana.

    a) What would be the angles on pie chart?

    b) Draw a pie chart to represent this information. 

    c) Use the pie chart to comment on these findings.

    3.3 Graph interpretation and Interpretation of statistical data

    Activity 3.3

    The graph below shows the sizes of sweaters worn by 30 year 1 students 

    in a certain school. Observe it and interpret it by answering the questions 

    below it:

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    CONTENT SUMMARY 

    Once data has been collected, they may be presented or displayed in various ways including graphs. Such displays make it easier to interpret and compare the data.

    Examples 

     1) The bar graph shows the number of athletes who represented five African countries in an international championship.

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    a) What was the total number of athletes representing the five countries? 

    b) What was the smallest number of athletes representing one country? 

    c) What was the most number of athletes representing a country? 

    d) Represent the information on the graph on a frequency table.

    Solution: 

    We read the data on the graph: 

    a) Total number of athletes are: 18 + 10 + 22 + 6 + 16 = 72 athletes 

    b) 6 athletes 

    c) 22 athletes

    d) Representation of the given information on the graph on a frequency table

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    2) Use a scale vertical scale 2cm: 10 students and Horizontal scale 2cm: 10 

    represented on histogram below to answers the questions that follows

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    a) Estimate the mode

    b) Calculate the range

    Solution: 

    a) To estimate the mode graphically, we identify the bar that represents 

    the highest frequency. The mass with the highest frequency is 60 kg. 

    It represents the mode.

    b) The highest mass = 67 kg and the lowest mass = 57 kg 

    Then, The range=highest mass-lowest mass=67 57 10 kg kg kg

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    3.4 Measures of central tendencies for ungrouped data

    Activity 3.4 

    Conduct a research in the library or on the internet and explain measures 

    of central tendency, their types and provide examples. 

    Insist on explaining how to determine the Mean, Mode, Median and their role 

    when interpreting statistic data.

    CONTENT SUMMARY 

    Measures of central tendency were studies in S1 and S2. 

     1. The mean 

    The mean, also known as the arithmetic average, is found by adding the values of the data and dividing by the total number of values. Suppose that a fruit seller earned the flowing money from Monday to Friday respectively: 300, 200, 600, 500, and 400 Rwandan francs. The mean of this money explains the same daily amount of money that she should earn to totalize the same amount in 5 days.

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    Where: 

    L: the lower limit of the modal class 

    fm: the modal frequency 

    f1: the frequency of the immediate class below the modal class 

    f2: the frequency of the immediate class above the modal class 

    w: modal class width. 

    Example:

    Find the modal class for the frequency distribution of kilometers that 20 

    runners ran in one week.

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    CONTENT SUMMARY

    The word dispersion has a technical meaning in statistics. The average 

    measures the center of the data. It is one aspect of observations. Another 

    feature of the observations is how the observations are spread about the 

    center. The observation may be close to the center or they may be spread 

    away from the center. If the observation are close to the center (usually 

    the arithmetic mean or median), we say that dispersion, scatter or variation 

    is small. If the observations are spread away from the center, we say that 

    dispersion is large.

    The study of dispersion is very important in statistical data. If in a certain 

    factory there is consistence in the wages of workers, the workers will be 

    satisfied. But if some workers have high wages and some have low wages, 

    there will be unrest among the low paid workers and they might go on strikes 

    and arrange demonstrations. If in a certain country some people are very 

    poor and some are very high rich, we say there is economic disparity. It 

    means that dispersion is large. 

    The extent or degree in which data tend to spread around an average is also 

    called the dispersion or variation. Measures of dispersion help us in studying 

    the extent to which observations are scattered around the average or central 

    value. Such measures are helpful in comparing two or more sets of data with 

    regard to their variability.

    Properties of a good measure of dispersion

    i) It should be simple to calculate and easy to understand

    ii) It should be rigidly defined

    iii) Its computation be based on all the observations

    iv) It should be amenable to further algebraic treatment

    Some measures of dispersion are Quartiles, variance, Range, standard 

    deviation, coefficient of variation. 

    1. Quartile 

    A measure which divides any array into four equal parts is known as quartile. 

    Each proportion contains equal number of items. The fist and the second 

    and the third points are termed as first quartile. The first quartile has 25% of 

    the items of the distribution below it and 75% of the items are greater than it. 

    The second quartile which is the median has 50% of the observations above 

    it and 50% of the observations below it. For the arranged data in ascending 

    order and quartiles are calculated as follows:

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    With observation, data are collected through direct observation. Information 

    could also be collected using an existing table that shows types of data to 

    collect in a certain period of time, this method of collecting data is reliable 

    and accurate.

    Once data has been collected, they may be presented or displayed in various 

    ways. Such displays make it easier to interpret and compare the data. 

    After the collection of data there is need of interpreting them and here there 

    are some tips:

    – Collect your data and make it as clean as possible.

    – Choose the type of analysis to perform: qualitative or quantitative

    – Analyze the data through various statistical methods such as mean, 

    mode, standard deviation or Frequency distribution tables

    – Reflect on your own thinking and reasoning and analyze your data and 

    then interpret them referring to the reality. 

    During interpretation, avoid subjective bias, false information and inaccurate 

    decisions.

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