Basic Statistics

PROBLEMS 185

Year Death Rate from Firearms

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

18.3

19.7

19.1

20.5

21.4

23.6

25.2

24.9

26.4

26.0

23.4

(a) State which model (single-sample or fixed-X) this data set is.

(b) Plot a scatter diagram and compute the regression line.

(c) Compute 95% confidence intervals for /3 and test the HO : P = 0.

12.2 Use the following data on length of service in days (X) and cost per day in
dollars (Y) for 10 patients on a home health care program.

Patient Number Length of Service, X Cost per Day, Y

1 2 3 4 5 6 I 8 9

10

310

89

22

9

120

99

63

170

20

198

35.00

34.60

102.60

136.20

69.50

79.60

140.20

45.40

81.3

29.50

(a) State which model the data follow and plot the scatter diagram.

(b) Do you expect the r to be positive or negative from looking at the scatter

(c) Give a 95% confidence interval for p.

(d) Test the Ho : p = 0 and HO : 0 = 0. Did you get the same P value?

12.3 In Problem 7.9 data are presented on counts of bacteria on 12 plates by two ob-

servers. Both observers counted the same plate and their counts were recorded.

In Problem 7.9, a confidence interval was computed on the difference in the

mean counts. The confidence limits did not include 0.

(a) Plot a scatter diagram of this data and compute r.

diagram? Should b be positive or negative?