A company produces electric devices operated by a thermostatic control

A company produces electric devices operated by a thermostatic control. The variance of the temperature at which these controls should operate should not exceed 4.0 degrees Fahrenheit. For a random sample of 20 of these controls, the sample variance of operating temperatures was 5.7 degrees. Is there evidence at the 5% significance level that the population variance exceeds the desired limit?

1. The test statistic for testing this claim will have the following distribution:

a) Chi-squared with 20 degrees of freedom

b) Z distribution

c) t distribution with 19 degrees of freedom

d) Chi-squared with 19 degrees of freedom

 

2. The value of the test statistic for testing the claim is _______________

3. The p-value associated with the test statistic is __________________

4. Based on your results, what is your conclusion?

a) Do not reject the null hypothesis and conclude that the population variance is greater than 4.

b) Do not reject the null hypothesis, there is Insufficient evidence that the population variance is greater than 4.

c) Reject the null hypothesis and conclude that the population variance is greater than 4.

d) Reject the null hypothesis, there is Insufficient evidence that the population variance is greater than 4.

5. Construct a 95% confidence interval for the true variance of operating temperature. The LCL is _______________

6. The UCL is _______________.