The following measurements were recorded for the drying time

The following measurements were recorded for the drying time, in hours, of a certain brand

of paint: 3.4, 2.5, 4.8, 2.9, 3.6, 2.8, 3.3, 5.6, 3.7, 2.8, 4.4, 4.0, 5.2, 3.0, 4.8

construct a 90% confidence interval for the true population mean using a suitable

statistical software.

Solution

Confidence Interval
CI = x ± t a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
ta/2 = t-table value
CI = Confidence Interval
Mean(x)=3.7867
Standard deviation( sd )=0.9709
Sample Size(n)=15
Confidence Interval = [ 3.7867 ± t a/2 ( 0.9709/ Sqrt ( 15) ) ]
= [ 3.7867 - 1.761 * (0.251) , 3.7867 + 1.761 * (0.251) ]
= [ 3.345,4.228 ]