According to a spring 2009 poll of more than 2,200 college students across 40 co

Question

According to a spring 2009 poll of more than 2,200 college students across 40 colleges and Universities, 70 percent of students reported feeling stressed on a daily basis. Assume that the true proportion of students who feel stressed on a daily basis is 70%.

1. Find two z scores that contain the central 95% of the standard normal distribution.

Lower:

Upper:

2. Suppose you take a survey of 104 college students. Between what two values will the sample proportion of students in the survey who feel stressed be between 95% of the time?

Lower:

Upper:

Explanation / Answer

Pr(Students feeling stressed) = 0.70

1. Here for to contain central 95% of the standard normal distribution.

lowe Z = -1.96

Upper Z = 1.96

2. Here n = 104

Here lower proportion = p^ - 1.96 * sqrt [p^ * (1-p^)/N] = 0.70 - 1.96 * sqrt (0.7 * 0.3/104) = 0.612

Upper proportion = p^ - 1.96 * sqrt [p^ * (1-p^)/N] = 0.70 + 1.96 * sqrt (0.7 * 0.3/104) = 0.788

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