Explanation Definition: 1. While computing the mean of a frequency distribution, write all products x ⋅ f of the values and their frequencies in a new column of the table. Represent the sum of these products by ∑ ( x ⋅ f ) . Denote the sum of the frequencies by ∑ f . The mean is then ∑ ( x ⋅ f ) ∑ f . 2. If x is a data value in a set whose mean is x ¯ , then x − x ¯ is called x’s deviation from the mean. 3. We denote the standard deviation of a sample of n data values by s = ∑ ( x − x ¯ ) 2 n − 1 . 4. We calculate the standard deviation, s, of a sample that is given as a frequency distribution as s = ∑ ( x − x ¯ ) 2 ⋅ f n − 1 . Here f is the frequency of data value x , and n = ∑ f is the number of data values in the distribution. Calculation: Observe the figure carefully. Notice that the grades depend upon the mean and the standard deviation. To determine the grade we will first determine the mean and standard deviation. From the given diagram understand the frequency of each data value. Average value x Frequency f 80 2 75 1 81 1 83 1 78 1 84 1 77 1 76 1 First find the mean of the given data set. To compute the mean, let us find all products x ⋅ f of the given values and their respective frequencies. For x = 80 and f = 2 , the product x ⋅ f = 80 ⋅ 2 = 160. For x = 75 and f = 1 , the product x ⋅ f = 75 ⋅ 1 = 75. For x = 81 and f = 1 , the product x ⋅ f = 81 ⋅ 1 = 81. For x = 83 and f = 1 , the product x ⋅ f = 83 ⋅ 1 = 83. For x = 78 and f = 1 , the product x ⋅ f = 78 ⋅ 1 = 78. For x = 84 and f = 1 , the product x ⋅ f = 84 ⋅ 1 = 84. For x = 77 and f = 1 , the product x ⋅ f = 77 ⋅ 1 = 77. For x = 76 and f = 1 , the product x ⋅ f = 76 ⋅ 1 = 76. The sum of these products is 160 + 75 + 81 + 83 + 78 + 84 + 77 + 76 = 714. Therefore, ∑ ( x ⋅ f ) = 714. The sum of the frequencies is 2 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 9. Therefore, ∑ f = 10. The mean is then ∑ ( x ⋅ f ) ∑ f = 714 9 = 79.3333333333333. Next find the standard deviation. To begin with, find the deviation from the mean for each value. For x = 80 the deviation from the mean is x ⋅ x ¯ = 80 − 79.3333333333333 = 0.6666666666667. For x = 75 the deviation from the mean is x ⋅ x ¯ = 75 − 79.3333333333333 = − 4.3333333333333. For x = 81 the deviation from the mean is x ⋅ x ¯ = 81 − 79.3333333333333 = 1.6666666666667. For x = 83 the deviation from the mean is x ⋅ x ¯ = 83 − 79.3333333333333 = 3.6666666666667. For x = 78 the deviation from the mean is x ⋅ x ¯ = 78 − 79

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ISBN: 9780134506470

Author: Pirnot

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Chapter 14.3, Problem 29E

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The number of As assigned using the given diagram, if the averages in the class are 80, 75, 81, 83, 80, 78, 84, 77, and 76

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Chapter 14.3, Problem 28E

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The number of As assigned using the given diagram, if the averages in the class are 80, 75, 81, 83, 80, 78, 84, 77, and 76

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To find: The number of As assigned using the given diagram, if the averages in the class are 80, 75, 81, 83, 80, 78, 84, 77, and 76

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To find:

The number of As assigned using the given diagram, if the averages in the class are 80, 75, 81, 83, 80, 78, 84, 77, and 76