Question 1193651
Ho: mean is 81.7 or higher
Ha: mean is <81.7
alpha=0.05 p{reject Ho|Ho true}
test is a z (0.95)
critical value is z<-1.645
calculation z=diff in mean/SE=-2.1/8.5/sqrt(100)
=-21/8.5=-2.47
reject Ho: there is a significant difference at the 5% level and the population should be considered to have an average less than 81.7
p-value =  0.007, well < 0.05.