In: Statistics and Probability
An engineer measured the Brinnel hardness of 25 pieces of ductile iron. The average hardness was 172.52. The population standard deviation of Brinnel Hardness of ductile iron is 10.31. The engineer hypothesized the the mean Brinnel hardness of such ductile pieces is greater than 170. Test this hypothesis for a = 0.05.
Solution :
= 170
=172.52
=10.31
n = 25
This is the right tailed test .
The null and alternative hypothesis is ,
H0 : = 170
Ha : > 170
Test statistic = z
= ( - ) / / n
= (172.52-170) / 10.31 / 20
= 0.05
Test statistic = z = 0.05
P(z > 0.05 ) = 1 - P(z < 0.05 ) = 1 - 0.5199
P-value =0.4801
= 0.05
P-value >
0.4801 > 0.05
Fail to reject the null hypothesis .
There is not sufficient evidence to suggest that