Question 918679
Ho: p = 0.15 claim
Ha: p ≠  .15


-----------------------------------------

sample proportion = p-hat = 40/234 = 0.17
---
test stat:: z(0.17) = (0.17-0.15)/sqrt[0.15*0.85/234] = .02 /.0233 = .8568
-----
5% significance level, critical value =  ±  1.96 
---------------------
Conclusiion: 
Since .8568 < 1.96, accept the average of 15%.
The test results have not shown sufficient evidence to support it has changed.