Question 928128
Ho: u = 8min 
Ha: u < 8min (claim)
.......
sample of 20: mean of 6.4 minutes with a sample standard deviation of 2.1 minutes. 
t(6.4) = -1.6/(2.1/sqrt(20)) = -3.407
p-value = tcdf(-100, -3.407, 19) = .0015
.......
confidence level .01
.0015< .01
Test results rejects Ho and supports retailer's claim