Question

Calculate an 80% CI for mean US population height (in inches),using your heights.Heights of individuals in US is normally distributed.

Heights are 6ft 1, 5 ft 2, and 5 ft 5

Answer 1

Solution:

We have to find 80% CI for mean US population height (in inches).

Heights of individuals in US is normally distributed.

Heights are 6ft 1, 5 ft 2, and 5 ft 5

First we need to convert these heights in inches,

1 foot = 12 inches

thus we get:

Height in foot	Calculations	Height in inches
6ft 1	=6x12 + 1 =	73
5ft 2	=5x12 + 2 =	62
5ft 5	=5x12 + 5 =	65

Formula:

where

Thus we need to make following table:

x: Height in inches	x^2
73	5329
62	3844
65	4225

Thus we get:

and

t_c is t critical value for c = 80% confidence level

df = n - 1= 3 - 1 = 2

two tail area = 1 - 0.80 = 0.20

t_c = 1.886

Thus

Thus 80% confidence interval is:

Thus 80% CI for mean US population height (in inches) , is .