Posted by **Mary** on Friday, May 18, 2012 at 5:05pm.

From random sample of 200 college students, 40 students indicated that they smoke cigarettes. Use the information from the sample to calculate a 95% confidence interval for the population proportion of college students that smoke cigarettes (round to nearest hundredth).

A. (0.14, 0.26)

B. (38, 42)

C. (0.17, 0.23)

D. (0.16, 0.24)

- Statistics -
**MathGuru**, Friday, May 18, 2012 at 7:22pm
Formula:

CI95 = p ± (1.96)[√(pq/n)]

...where p = x/n, q = 1 - p, and n = sample size.

Note: ± 1.96 represents 95% confidence interval using a z-table.

For p in your problem: 40/200 = 0.2

For q: 1 - p = 1 - 0.2 = 0.8

n = 200

I let you take it from here to calculate the interval and determine your answer from the selections given.

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