Question

Determine the margin of error for a confidence interval to estimate the population mean with nequals25 and s​ = 12.7 for the confidence levels below. ​a) 80​% ​b) 90​% ​c) 99​% ​a) The margin of error for an 80​% confidence interval is _.

Answer 1

Solution :

(a) At 80%

t _/2,df = 1.318

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

= 1.318 * (12.7 / 25)

Margin of error = E = 3.35

(b)

At 90%

t _/2,df = 1.711

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

= 1.711 * (12.7 / 25)

Margin of error = E = 4.35

(b)

At 99%

t _/2,df = 2.797

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

= 2.797 * (12.7 / 25)

Margin of error = E = 7.10