1. Frequency and Stem - Leaf plot
Our lesson
Frequency and Stem - Leaf plot
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2. Warm Up
Find the area of a parallelogram whose base is 35 in. and the corresponding height is 12in.
2. Find the base of the triangle whose area is 48 in2 and height is 12 in.
3. Find the circumference of a circle with a diameter of 14cm.
4. The 3D figure Octagonal Prism
a) How many vertices does it have?
b) How many edges does it have?
5. Find the volume of the rectangular prism whose length is 4 in, width 7 in and height 4 in.
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3. Area of Parallelograms
1. Parallelogram is a quadrilateral in which pairs of opposite sides are parallel.
2. The distance between the pairs of opposite sides of a parallelogram is called an altitude of the parallelogram.
3. The opposite sides and opposite angles of a parallelogram are equal.
Area of the parallelogram is equal to the product of one of its bases and the corresponding altitude.
i.e. A = b * h
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4. Area of Triangles ½ x b x h
A triangle is a kind of polygon that has three sides.
The area of a triangle is given by "half of base times height“.
Area =
where b  is the length of the base. h  is the height of the triangle.
½ x b x h
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5. Area of Trapezoids Area of trapezoid, A = 1/2 * h (b1 + b2)
Trapezoid is a quadrilateral in which one pair of opposite sides are parallel.
The two parallel sides of a trapezoid are its bases, the two non parallel sides are its legs. B A C D F E
Area of trapezoid, A = 1/2 * h (b1 + b2)
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6. Area and Circumference of Circles
A circle is a set of points in a plane at a fixed distance from a fixed point.
The fixed point is called the center of the circle
The perimeter of the circle is called the circumference of the circle
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7. 3D figures 3D figures are figures which have length, width and height.
In the term 3D, 3 refers to the numbers of dimensions and D refers to dimension
Cube
Cylinder
Square Pyramid
Cone
Sphere
Rectangular Prism
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8. surface area of a cylinder = 2*r2 + 2rh
Surface Area of Prism and Cylinder
Surface Area of a Prism
The surface area of a prism is the sum of the areas of
all the sides of the prism. The formula for the surface
area of a prism therefore depends on the type of prism.
Surface Area of a Cylinder
The surface area of a cylinder is the sum of the areas
of the two bases and the lateral face of the cylinder.
surface area of a cylinder = 2*r2 + 2rh
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9. Volume = length × width × height Volume = π(radius)2x height
Volume of Rectangular Prism
& Cylinder
The amount of space occupied by an object is called its volume.
The volume of a rectangular prism is given by the formula:
Volume = length × width × height
The volume of a cylinder is given by the formula:
Volume = π(radius)2x height
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10. Frequency - Introduction
Statisticians collect data and process it in order to produce useful information. Each information collected is an observation. Information collected at the beginning stage consists of only raw data. Before any conclusions can be drawn from such data, it must be condensed and arranged in usable form.
In the raw data, there can be repetitions of observations. The number of times a particular observation repeats itself is called its frequency.
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11. Similarly, the frequency of 47 is 2
Example: The marks scored by 10 students in a mathematics test is as follows.
In the above example, you can see that the score 55 is repeated 3 times. So, the frequency of 55 is 3
Similarly, the frequency of 47 is 2
Marks Obtained
Frequency 47 2 50 1 51 55 3 62 64
Total 10
Let us distribute the data in the example by finding the frequency of all observations and rearranging them, starting from the lowest to the highest observation (or highest to the lowest observation) in a table as given at the left
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12. Frequency Distribution
This representation is called as Frequency Distribution Table or Frequency Table of marks of 10 students in a class.
In the table, you can see that sum of all frequencies is equal to the number of observations.
The table is useful, as it gives important features of the raw data at a quick glance.
Marks Obtained
Frequency 47 2 50 1 51 55 3 62 64
Total 10
The score 55 has the maximum frequency of 3.
So, we can immediately say that the average score of students in the math’s test is is 55
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13. Finding frequencies using tally marks
When the number of observation is limited, counting and finding the frequencies is easy. However, when the number of observations is large, it may not be convenient to find the frequencies by simple counting.
In such cases, Tally Marks are used to find the frequencies.Tallies are usually marked in bunches of five for ease in Counting. The fifth tally in a bunch is usually marked diagonally across the earlier four. .
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14. Example: Write the tally marks for the following frequencies.
a) b) c) 5 d) 7
The table below shows the tally marks for the above frequencies
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15. Frequency distribution using tally marks
Let us consider an example.
Following are the heights (in cm) of of 30 girls in a class.
140, 140, 160,139, 153, 153, 146, 150, 148, 150, 152, 154, 146, 160, 150,
148, 148, 150, 148, 140, 138, 153, 152, 150, 148, 138, 140, 152, 148, 146
Prepare a frequency distribution for the above data and also the mean.
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16. First make a table with four rows.
In the first row, write all the observations(x) i.e the heights of girls in ascending (or descending) order.
In the second row, keep putting the tally marks against each observation.
Once all the observations is exhausted, count the tally marks against each height and write the number in the frequency column.
Sum up all the frequencies (F), to get total number of observations.
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17. To find the mean of a frequency distribution, let us
go through the following steps.
Multiply each observation (X) by its frequency (F)
Find the sum of the products (F *X) obtained in step 1 and write it in
Divide the sum obtained (F *X) by the sum of all frequencies (F) to get the required Mean
Thus we can arrive at the following frequency
distribution table.
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18. Frequency distribution of the heights of 30 girls
Mean of a Frequency distribution
Frequency distribution of the heights of 30 girls
Now we can determine the mean of the frequency distribution of heights of 30 girls using the following formula,
Sum of (F * X)
Sum of (F)
Mean =
4440 30 =
= 148
So, the average height of 30 girls is 148 cm
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19. Grouping of data Organizing data in a table in terms of frequencies
is known as the ungrouped frequency distribution of
raw data. When the number of observations is quite
large, it becomes necessary to condense the given
data into several groups and obtain a frequency
distribution of the number of observations falling in
each group. In such a case, the data is said to be
grouped and the distribution obtained is called a
grouped frequency distribution.
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20. Grouped Frequency Distribution
Grouping of data is done by going through the following steps.
Find out the difference between the highest and lowest values of the observation. The value obtained is called the Range.
2. Depending upon the range, condense the observations into different groups.Each of these groups is called a Class Interval or a Class.
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21. Usually the number of classes will be kept between 5 & 15.
The lower value of a class interval is called its Lower Class Boundary and upper value of a class interval is called its Upper Class Boundary. The sum of the lower and upper limits of the class divided by two is called the Midpoint of the class or the Class Mark
Usually the number of classes will be kept between 5 & 15.
3.The difference between the upper and the lower limit of a class is called the Size or Width of the Class Interval. It is obtained by dividing the range by the number of classes. The quotient obtained gives approximate size of a class and a convenient number around the quotient can be chosen.
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22. Grouped Frequency Distribution - example
Example: The weight(in kg) of 25 athletes are given below:
67, 83, 74, 81, 67, 84, 61, 54, 59, 60, 36, 45,
55, 58, 75, 57, 39, 49, 73, 77, 58, 63, 44, 88, 52
Construct a group frequency table
1) First, find the range: The maximum and minimum number in the data are 88 and 36 respectively.So, Range = 88 –36 =52
2) Decide the number of classes:As the range is 52, let us decide that the number of classes be 6.
3) Determine the size of Class: Range/number of classes. Size of the class = 52/6 = Let the size be 10
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23. Ensure that the classes include the minimum and maximum number occurring in the data. Minimum number 36 belongs to the class 35 –44 and the maximum number belongs to the class Thus, the following group frequency table can be obtained.
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24. Stem and Leaf Plot
Data can be shown in a variety of ways including graphs, charts and tables. A Stem and Leaf Plot is a type of graph which summarizes the shape of a set of data (the distribution) and provides extra detail regarding individual values. Here, the data is arranged by place value.
The digits in the largest place is referred to as the stem and the digits in the smallest place are referred to as the leaf (leaves). The leaves are always displayed to the left of the stem. Stem and Leaf Plots are great organizers for large amounts of information.The main advantage of a stem and leaf plot is that the data are grouped and all the original data are shown.
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25. The stem is the first digit or digits;
To make a stem and leaf plot, each observed value must first be separated into its two parts:
The stem is the first digit or digits;
The leaf is the final digit of a value;
Each stem can consist of any number of digits; but
Each leaf can have only a single digit
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26. How to draw a Stem and Leaf plot ?
On the left hand side of the page, write down the thousands, hundreds or tens (all digits but the last one). These will be the stems.
Draw a line to the right of these stems.
3) On the other side of the line, write down the ones (the last digit of a number). These will be the leaves.
4) Finally put a legend or key on the plot to show what you mean by the numbers on this plot. .
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27. Suppose the observed values are 5, 40, 278 and 45.7.
The stem and leaf values for these are,
The stem is 0 and the leaf is 5
The stem is 4 and the leaf is 0
The stem is 27 and the leaf is 8
The stem is 45 and the leaf is 7.
If the range of values is too great, the number 45.7 can be rounded up to 46 to limit the number of stems
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28. Making a Stem and Leaf plot
Let us consider an example to draw a stem and leaf plot.
A teacher asked 10 of her students how many books they had read in the last 12 months. Their answers were as follows:
12, 23, 19, 6, 10, 7, 15, 25, 21, 12
Prepare a stem and leaf plot for these data.
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29. The stem and leaf plot for the above set of data will be as shown below.
Key: 2|3 = 23
Stem 0 represents the class interval 0 to 9;
Stem l represents the class interval 10 to 19;
Stem 2 represents the class interval 20 to 29.
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30. Ordered Stem and Leaf plot
An ordered stem and leaf plot is one whose leaves are arranged in ascending order from left to right. Also, in an ordered stem and leaf plot, leaves (digits) are notseparated with punctuation marks (commas or periods) since each leaf is always a single digit.
Consider the following example for making an ordered stem and leaf plot:
Fifteen people were asked how often they drove to work over 10 working days. The number of times each person drove was as follows:
5, 7, 9, 9, 3, 5, 1, 0, 0, 4, 3, 7, 2, 9, 8
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31. Ordered stem and leaf plot for the above data is as shown below.
Key: 0|3 = 3
The disadvatage here is that this stem and leaf plot does not give much information about the data. With only one stem, the leaves are overcrowded.
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32. Splitting the stems in an ordered Stem and Leaf plot
Suppose in an ordered stem and leaf plot, if the leaves become too crowded, then it might be useful to split each stem into two or more components to give much more information about the data.
Let us split the stems in the previous example as given below .
You can split the stem 0–9 into two intervals of 0–4 and 5–9. or
You can also split the stem 0–9 into five intervals: 0–1, 2–3, 4–5, 6–7 and 8–9.
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33. Stem and leaf plot of 2 intervals
Key: 0|5 = 5
Stem and leaf plot of 2 intervals
The stem 0(0) means all the data within the interval 0–4.
The stem 0(5) means all the data within the interval 5–9.
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34. Splitting the stems in an ordered stem and leaf plot
Stem and leaf plot of 5 intervals
Key:0 | 4 = 4
The stem 0(0) means all the data within the interval 0–1.
The stem 0(2) means all the data within the interval 2-3.
The stem 0(4) means all the data within the interval 4-5.
The stem 0(6) means all the data within the interval 6-7.
The stem 0(8) means all the data within the interval 8-9.
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35. Outliers
An outlier is an extreme value of the data. It is an observation value that is significantly different from the rest of the data. There may be more than one outlier in a set of data.
Sometimes, outliers are significant pieces of information and should not be ignored. Other times, they occur because of an error or misinformation and should be ignored.
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36. Back to Back Stem and Leaf plot
Suppose we have two sets of data to compare. Then we can use a 'back to back' Stem and Leaf Plot.
For example, you want to compare the scores of two sports teams,
Team A 30, 57, 37, 33, 59, 42, 39, 48, 53, 51
Team B 32,45, 58, 59, 32, 45, 43, 54, 56, 58
 Write the Stem and Leaf Plot for the above data.
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37. Back to Back Stem and Leaf plot
Key: 4|8 = 48
The tens column is now in the middle and the ones column is to the right and left of the stem column. You can see that the Team B had more games with a higher score than the Team A.
The Team B had only 2 games with a score of 32. The Team A had 4 games with scores 30, 33, 37 and 39. You can also see that the Team B had the highest score of all i.e 59, compared to the Team A with a 57.
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38. Your Turn What is the frequency denoted by these tallies? a) b) c)
Find the range of the following scores.
23, 25, 22, 19, 22, 25, 26, 18, 20, 23, 21, 24, 16
Find the lower limit and upper limits of the class intervals
a) 10 – b) 0- 5, 5 -10
Find the size of the class intervals
a) 35 – b) 85-94
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39. Your Turn Find the class mark of the following classes.
a) 20 – b) 50 –59
6. Find the approximate average score from the following frequency distribution table.
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40. Your Turn
Following are the set of data which are the high temperatures recorded for 30 consecutive days. Summarize this data by creating a frequency distribution of the temperatures.
50, 45, 49, 50, 43, 49, 50, 49, 45, 49, 47, 47, 44, 51, 51, 44, 47, 46, 50, 44, 51, 49, 43, 43,49, 45, 46, 45, 51, 46
8. Following is the attendance of grade 8th of a school for 28 days out of 80 students in the class .Make a frequency distribution table taking the first group as
31, 41, 49, 53, 54, 55, 55, 57, 61, 61, 62, 63, 63, 63, 64, 64, 66, 66, 67, 69, 70, 71, 71, 75, 75, 75, 77, 78
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41. Your Turn
Imagine that your school baseball team scores the following number of home runs in 10 games:
4, 5, 8, 5, 7, 8, 9, 8, 8, 7
Make a frequency distribution table for the above data and find the mean
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42. Your Turn
10. Britney is a swimmer training for a competition. The number of
50-metre laps she swam each day for 30 days are as follows:
22, 21, 24, 19, 27, 28, 24, 25, 29, 28, 26, 31, 28, 27, 22,39,20,10, 26, 24, 27, 28, 26, 28, 18, 32, 29, 25, 31, 2
a) Prepare an ordered stem and leaf plot. Make a brief comment onwhat it shows.
b) Redraw the stem and leaf plot by splitting the stems into five-unit intervals. Make a brief comment on what the new plot shows.
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43. Refreshment time
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44. Click on the boy to play a game
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45. Q 1.The marks obtained by 20 students in Science during an half yearly examination is as follows.
48, 59, 64, 34, 59, 36, 73, 64, 79, 39,
59, 62, 67, 59, 91 31, 59, 73, 67, 77
Prepare a frequency distribution table for the above data and also find the Mean.
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46. With reference to the table, determine
Q 2.Study the following table which shows a frequency distribution of marks of 60 students who appeared in an examination.
With reference to the table, determine
The lower limit of the sixth class
The upper limit of the fourth class
c) The class mark of the third class
d) The size of the fifth class
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47. Q 3.The weights (to the nearest tenth of a kilogram) of 30 students were measured and recorded as follows:
59.2, 61.5, 62.3, 61.4, 60.9, 59.8, 60.5, 59.0, 61.1, 60.7, 61.6, 56.3, 61.9, 65.7, 60.4, 58.9, 59.0, 61.2, 62.1, 61.4, 58.4, 60.8, 60.2, 62.7, 60.0, 59.3, 61.9, 61.7, 58.4, 62.2
Prepare an ordered stem and leaf plot for the data. Briefly comment on what the analysis shows?
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48. Let’s summarize what we have learnt today
Observations gathered at the beginning stage constitutes the raw data.
Frequency denotes the number of times a particular observation occurs in a given data
The difference between the highest and lowest values of the observations is known as the range.
Frequency distribution is a table showing the frequencies of the various observations of a data.
Tally marks are used to find the frequencies when the number of observations is large.
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49. Let’s summarize what we have learnt today
When the number of observations is very large, the data is usually organized into groups called class intervals and the data obtained is called the grouped data.
7. The lower value of a class interval is called its lower limit and upper value of a class interval is called its upper limit.
8. The difference between the upper and lower class limits is called the width or size of the class interval.
9. The mid value of a class interval is called its class mark.
10. A Stem and Leaf Plot is a type of graph that summarizes the shape of a set of data (the distribution) and provides extra detail regarding individual values.
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50. Let’s summarize what we have learnt today
11. The digits in the largest place is referred to as the stem and the digits in the smallest place are referred to as the leaf (leaves)
12. In an ordered stem and leaf plot, the leaves are arranged in ascending order from left to right.
An outlier is an extreme value of the data. It is an observation value that is significantly different from the rest of the data.
One can use a back to back stem and leaf plot while comparing two sets of data.
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51. Learn as much as you can while you are young
You did a great job !
Learn as much as you can while you are young
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