Statistics
posted by Mary
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)

MathGuru
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 ztable.
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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