Question

The average tensile strength of carbon fiber cloth is 600 MPa. You are testing a new weaving pattern for the carbon fiber threads and want to know if this new weave causes a difference in the tensile strength. After testing 18 samples of the new weave, you found a sample average of 585 MPa with a standard deviation of 34 MPa. At a significance level of 0.05, test to see if this new weave has a different mean than 600 MPa.

Answer 1

This is the two tailed test .

The null and alternative hypothesis is

H₀ : = 600

H_a : 600

Test statistic = t

= ( - ) / s / n

= (585 - 600) / 34 / 18

= -1.872

Test statistic = -1.872

df = 17

P-value = 0.0785

= 0.05

P-value >

Fail to reject the null hypothesis .