Number of observations is 25 The sample mean is 185 and the

Number of observations is 25. The sample mean is .185 and the standard deviation (sigma) is 3.2. What is the 97 percent confidence interval?

Solution

mean = 0.185

n=25

SD = 3.2

z for 97% CI = 1.88

Margin of error = (z*SD)/sqrt(25) = ( 1.88 * 3.2)/ sqrt(25) = 1.2

Therefore CI :

( 0.185 - 1.2 , 0.185 + 1.2)

= ( -1.015 , 1.385 ) Answer