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 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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