Question 1065076
The sample mean is 12480 and the sample standard deviation is 2000
:
We want a 90% confidence interval for the population mean
:
alpha(a) is 1 - (90/100) = 0.10
:
critical probability(p*) = 1 - (a/2) = 0.95
:
because our sample size is < 30, we use the t-statistic
:
degrees of freedom = 9 - 1 = 8
:
we lookup in the students t-table the critical value(CV) that has 8 degrees of freedom and a p* of 0.95
:
CV is 1.860
:
margin of error(ME) = CV * standard deviation = 1.860 * 2000 = 3720
:
***********************************************************
95% confidence interval = 12480 + or - 3720 = (8760, 16200)
***********************************************************
: