Question

Is smoking during pregnancy associated with premature births? To investigate this question, researchers selected a random sample of 107 pregnant women who were smokers. The average pregnancy length for this sample of smokers was 264 days. From a large body of research, it is known that length of human pregnancy has a standard deviation of 16 days. The researchers assume that smoking does not affect the variability in pregnancy length. Find the 99% confidence interval to estimate the length of pregnancy for women who smoke.

(Note: The critical z-value to use, zc, is: 2.576)

Answer 1

Solution:-

Given that,

Sample mean

Sample Size n=107

Standard Deviation

Standard error

.

For 99% CI Value of Z is =2.576.

margin of Error E=Z*Standard error

=2.576*1.547=3.98.

Lower Bound=smple mean-E

=264-3.98=260.02

Lower Bound=260.02.

Upper Bound= Sample Mean+E

=264+3.98=267.98

Upper Bound=267.98.

From Above 99% Confidence Interval For Population Mean=(260.02,267.98).