A calculus instructor uses computer aided instruction and allows students to tak

Question

A calculus instructor uses computer aided instruction and allows students to take the midterm exam as many times as needed until a passing grade is obtained. Following is a record of the number of students in a cla ss of 40 who took the test each number of times:

a. Find the expected value of the number of tests taken.

b. Compute the variance and the standard deviation of the number of tests taken.

      Students                 Number of Tests          20                     1          10                           2            7                           3            3                           4

Explanation / Answer

Each probability is between 0 and 1 and the sum is 1.00.

Relative frequency

Number of tests

.50

1

.35

2

.10

3

.05

4

m = 1.7

s 2 = .71

s = .8426

Relative frequency

Number of tests

.50

1

.35

2

.10

3

.05

4

m = 1.7

s 2 = .71

s = .8426

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