Question 1197696
Ho: u = 15 (claim)
Ha: u < 15
x̄ = 11.8 , s = 3.9, n = 12
0.05 level of significance level    

t(11.8) = {{{(11.8 - 15)/(3.9/sqrt(12))}}} = -2.842 rounded

one-tailed
p-value = P(z  ≤ -2.842)  = .008  Excel function:  =TDIST(t,degrees_freedom,tails), 
   .008 <.05  Reject Ho