1) In a study, temperature readings were taken at different locations in 1980 and in 2012. The average daily temperatures for the month of June in each of 41 different locations are listed below. We would like to see if there is any difference between the mean temperatures of 1980 and 2012. If you believe the populations are independent, then assume the population variances are equal.

Location	n	Average	Standard deviation
1980	41	82	12.1
2012	41	87	9.2
Difference (d = y1980 - y2012)	41	-5.0	5.8

Perform a statistical test. (a) What are the null and alternative hypotheses? H₀: H_A: (b) What is the test statistic?___________ (Round your answer to 3 decimal places, if needed.) (c) Using the statistical table, the p-value is__________ (0.01 < p-value < 0.02 0.02 < p-value < 0.05 0.05 < p-value < 0.10 0.10 < p-value < 0.20 p-value > 0.20 0 < p-value < 0.01 .) (d) Based on the p-value,__________ (reject or fail to reject ) the null hypothesis at the significance level of 0.02. (e) This data____________ (provides or does not provide) sufficient evidence to conclude that the mean temperature in 1980 is_____________ (less than or more than) different from the mean temperature in 2012.

2) A clinic compared healthy dogs it owned with healthy pets brought to clinic to be neutered. The summary statistics for blood cholesterol levels (milligrams deciliter of blood) appear in the following table:

Types	n	Average	Standard deviation
Pets (P)	61	198	69.8
Clinic (C)	61	173	43.8
Difference (d = P - C)	61	25.0	51.3

(a) Find a 90% confidence interval for the difference in mean blood cholesterol levels dogs brought to the clinic (P) and dogs owned by the clinic (C). (Round your answers to 4 decimal places, if needed.)

b) Based on this confidence interval, can we conclude there is some differences in mean blood cholesterol levels between the two groups?

a) Yes, since the interval contains 0.

b) Yes, since the interval is completely above 0.

c) No, since the interval is completely above 0.

d) No, since the interval contains 0.

3) It is believed that animals living in northern regions have shorter appendages than animals living in southern regions. Random samples of birds were selected from each group and wing lengths for birds (in millimeters) were measured. The following table gives summary statistics.

Region	n	Average	Standard deviation
Northern (N)	30	115.5	1.3
Southern (S)	30	116.7	2.7
Difference (d = N - S)	30	-1.2	1.2

(a) Find a 90% confidence interval for the mean difference of wing lengths of birds between the northern regions and the southern regions. (Round your answers to 4 decimal places, if needed.)

(b) Based on this confidence interval, is there enough evidence to support the belief?

a) Yes, since the interval is completely below 0.

b) No, since the interval is completely below 0.

c)Yes, since the interval contains 0.

d) No, since the interval contains 0.