1) Lily Energy Systems manufacturer's wood-burning heaters and fireplace inserts. One of its systems has an electric blower, which is...

1) Lily Energy Systems manufacturer's wood-burning heaters and fireplace inserts. One of its systems has an electric blower, which is thermostatically controlled. The blower is designed to automatically turn on when the temperature in the stove reaches 125°F and turn off at 85°F. Complaints from customers indicate that the thermostat control is not working properly. The company feels that the thermostat is acceptable if the variance in the cutoff temperature is less than or equal to 175. The company takes a sample of 24 thermostats and finds that the variance equals 289. The calculated chi-square test statistic and the table value for a 0.05 significance level are 

    A. 38.076, 38.99.

B. 37.983, 38.076.

C. 35.172, 38.99.

D. 37.983, 35.172.

I have put B

2)  In testing the difference between two population means using two independent samples, the sampling distribution of the sample mean difference x̄1 − x̄2 is normal if the 

    A. sizes are both greater than 30.

B. populations are nonnormal and the sample sizes are large.

C. populations are normal.

D. population sizes are both greater than 30.

I have put C

3) In testing for the equality of two population variances, when the populations are normally distributed, the 10% level of significance has been used. To determine the rejection region, it will be necessary to refer to the Ftable corresponding to an upper-tail area of 

    A. 0.90.

B. 0.20.

C. 0.10.

D. 0.05.

I have put C

Can you help me with these questions please?