Answer:
Confidence interval is 128±2.326 days (between 125.674 days and 130.326 days) in 90% confidence level
Step-by-step explanation:
Confidence interval can be calculated as M±ME where
- M is the average pregnancy days of smoking women and
- ME is the margin of error in 90% confidence level.
Margin of Error in 90% confidence level can be calculated using the formula:
ME= where
- z is the z-value in 90% confidence level (1.645)
- s is the standard deviation of pregnancy length (16)
- N is the sample size (128)
putting these numbers in the formula, we get:
ME= =2.326
then confidence interval is 128±2.326 ( between 125.674 and 130.326 ) in 90% confidence level