In: Statistics and Probability
Test the following claim. Identify the null hypothesis, alternative hypothesis, test statistic, P-value, conclusion about the null hypothesis, and final conclusion that addresses the original claim. A simple random sample of 60 screws supplied by a certain manufacturer is obtained, and the length of each screw is measured. The sample mean is found to be 0.622 in. Assume that the standard deviation of all such lengths is 0.016 in, and use a 0.01 significance level to test the claim that the screws have a mean length equal to 5 divided by 85/8 in (or 0.625 in), as indicated on the package labels. Do the screw lengths appear to be consistent with the package label?
2 Tailed Z test, Single Mean
Given: = 0.625 inches, = 0.622 inches meters, = 0.016 meters, n = 60, = 0.01
The Hypothesis:
H0: = 0.625: The mean length of the screws is equal to 0.625 inches meters. (Claim)
Ha: 0.625: The mean length of the screws is not equal to 0.625 inches.
This is a 2 tailed test
The Test Statistic: Since the population standard deviation is known and n > 30, we use the z test.
The test statistic is given by the equation:
t observed = -1.45
The p Value: The p value (2 tailed) for z = -1.45 is; p value = 0.1470
The Decision Rule: If P value is < , Then Reject H0.
The Decision: Since P value (0.1470) is > (0.01) , We Fail to Reject H0.
The Conclusion: Fail to reject H0.There is not sufficient evidence at the 99% significance level to warrant rejection of the claim that the mean length of the screws is equal to 0.625 inches