In Exercises 14.98-14.108, use the technology of your choice to do the following tasks.
a. Decide whether your can reasonably apply the conditional mean and predicted value t-interval procedures to the data. If so, then also do parts (b) - (h).
b. Determine and interpret a point estimate for the conditional mean of the response variable corresponding to the specified value of the predictor variable.
c. Find and interpret a 95% confidence interval for the conditional mean of the response variable corresponding to the specified value of the predictor variable.
d. Determine and interpret the predicted value of the response variable corresponding to the specified value of the predictor variable.
e. Find and interpret a 95% prediction interval for the value of the response variable corresponding to the specified value of the predictor variable.
f. Compare and discuss the differences between the confidence interval that you obtained in part (c) and the prediction interval that you obtained in part (e).

14.103 High and Low Temperature. The data from Exercise 14.31for average high and low temperatures in January of a random sample, of 50cities are on the WeissStats site. Specified value of the predictor variable: 55°F.

Short Answer

Expert verified

(a) Apply the conditional mean and predated value t-interval technique to the data seems reasonable.

(b) The conditional mean of the response variable corresponding to the predictor variable x=55is 42.85.

(c) The conditional mean of the response variable has a 95%confidence interval of (41.67,44.04).

(d) The predicted value of the score associated with the predicted variable is 42.85.

(e) A 95%confidence interval between 34.42and 51.28degrees for the low temperature with a mean high temperature of 55degrees.

(f) The prediction interval is greater than the confidence interval.

Step by step solution

01

Part (a) Step 1: Given information

To decide whether reasonably apply the conditional mean and predicted value t-interval procedures to the data.

02

Part (a) Step 2: Explanation

The data from Exercise 14.31 for average high and low temperatures in January of a random sample as follows:

HIGH
LOW

80
64
33
22

85
65
31
22

36
28
91
74

59
41
86
71

62
46
66
55

64
51
61
45

85
79
64
45

36
23
59
41

85
68
42
33

41
34
33
21

52
41
26
18

68
48
57
45

34
24
45
36

52
42
42
33

61
52
70
45

35
25
85
73

85
78
82
76

28
15
52
38

45
34
85
71

48
39
86
74

81
64
44
37

28
9
59
49

36
29
35
26

45
40
44
34

85
69
49
36



03

Part (a) Step 3: Explanation

The residual plot clearly shows that the residuals lie within the horizontal band.
It is obvious from the normal probability plot of residuals that the residuals follow a fairly linear trend.
Hence, the regression inference assumptions for the variables average high January temperature and average low January temperature are not violated.
As a result, implementing the conditional mean and predated value t-interval technique to the data seems reasonable.

04

Part (b) Step 1: Given information

To determine and interpret a point estimate for the conditional mean of the response variable corresponding to the specified value of the predictor variable.

05

Part (b) Step 2: Explanation

The MINITAB procedure as follows:
Step 1: Choose Stat >Regression>Regression.
Step 2: In Response, enter the column Low.
Step 3: In Predictors, enter the column High.
Step 4: In Options, enter 55 under Prediction interval for new observations.
Step 5: In Confidence Level, enter 95.
Step 6: In Storage, Choose Fits, Confidence limits, SEs of fits, and Prediction limits.
Step 7: Click OK.
And the MINITABoutput as follows:
The Prediction for LOW:

The conditional mean of the response variable corresponding to the predictor variable x=55is 42.85.

06

Part (c) Step 1: Given information

To find and interpret a 95%confidence interval for the conditional mean of the response variable corresponding to the specified value of the predictor variable.

07

Part (c) Step 2: Explanation

The 95 percent confidence interval for the conditional mean of the response variable corresponding to the predictor variable x=55is (41.67,44.04), according to theMINITAB output in part (b).
The conditional mean low temperature with a mean high temperature of 55degrees lies between 41.67and 44.04degrees, according to 95percent confidence.
As a result, the conditional mean of the response variable has a 95%confidence interval of (41.67,44.04).

08

Part (d) Step 1: Given information

To determine and interpret the predicted value of the response variable corresponding to the specified value of the predictor variable.

09

Part (d) Step 2: Explanation

The predicted value of the score corresponding to the predicted variable x=55 is 42.85, according to the MINITABoutput in part (b).
As a result, the predicted value of the score associated with the predicted variable is 42.85.

10

Part (e) Step 1: Given information

To find and interpret a 95% prediction interval for the value of the response variable corresponding to the specified value of the predictor variable.

11

Part (e) Step 2: Explanation

The 95percent prediction interval for the conditional mean of the response variable corresponding to the predictor variable x=55is (34.42,51.28), according to the MINITABoutput in part (b).
As a result, there is a 95%confidence interval between 34.42and 51.28degrees for the low temperature with a mean high temperature of 55 degrees.

12

Part (f) Step 1: Given information

To compare and discuss the differences between the confidence interval that obtained in part (c) and the prediction interval that obtained in part (e).

13

Part (f) Step 2: Explanation

Parts (c) and (e) show that the confidence interval and prediction interval are centered on the predicted value of 55 degrees for the mean high temperature.
In addition, the prediction interval exceeds the confidence interval.

As a result, the prediction interval is greater than the confidence interval.

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x
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