Question

If n = 28, x = 44, and s = 11, construct a confidence interval at a 80% confidence level. Assume the data came from a normally distributed population. Give your answers to three decimal places. < μμ <

Answer 1

Given that,

= 44

s =11

n = 28

Degrees of freedom = df = n - 1 = 28- 1 = 27

At 80% confidence level the t is ,

t /2,df = t0.10,27 = 1.314 ( using student t table)

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

= 1.314 * (11 / 28) = 2.732

The 90% confidence interval estimate of the population mean is,

- E < < + E

44 -2.732 < < 44 + 2.732

41.268 < < 46.732