Question

A metal casting process is designed to produce parts with a specified weight of 2.1 ounces. A sample of 30 parts yields a sample mean weight of 2.084 ounces. The researcher assumes that the process standard deviation is .05 ounces and is looking for evidence at the .05 level that the process is producing parts that are not 2.1 ounces on average.

Find:
A. Hypothesis
B. Test Statistic
C. P-value
D. Decision

E. Which of the following correctly describes the 95% confidence interval for the mean based on the sample?

A.	The interval includes only irrational numbers
	B.	The interval includes only values less than 2.1
	C.	The interval includes only values greater than 2.1
	D.	The interval includes the value 2.1

Answer 1

A. Here the claim is that the process is producing parts that are not 2.1

So the hypothesis is vs

B. Here it is given that researcher assumes that the process standard deviation is .05 ounces, which means population standard deviation is known so we will use z distribution

Also it is given that sample mean weight is 2.084 ounces.

So test statistics is

c. P value for 2 tailed test is

d. As P value is greater than , we fail to reject the null hypothesis

Hence we conclude that the process is producing parts that are 2.1.