Question

Imagine we sampled 9 people. The sample mean of cigarettes per week was 5. The sample standard deviation was 2. What is the 95% confidence interval for the true mean of cigarettes per week? Show work.

Answer 1

Solution :

t _/2,df = 2.306

Margin of error = E = t_/2,df * (s /n)

= 2.306 * (2 / 9)

Margin of error = E = 1.54

The 95% confidence interval estimate of the population mean is,

- E < < + E

5 - 1.54 < < 5 + 1.54

3.46 < < 5.54

(3.46 , 5.54)