Question

a smoking researcher is interested in estimating the average age when cigarette smokers first began to smoke. Taking a random sample of 25, she determines a sample mean of 16.8 years and a sample deviation of 1.5 years. Construct a 95% confidence interval to estimate the population mean age of the onset of smoking

Answer 1

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.025) and its Z score.

95% = mean ± Z SEm

SEm = SD/√n

Answer 2

83.2