HW 4 Solution - Statistics 106 Homework 4 Solution Not Due...

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Statistics 106 Homework 4 Solution Not Due 18.6 Refer to Rehabilitation therapy Problem 16.9. a. Obtain the residuals and prepare aligned residual dot plots by factor level. What departures from ANOVA model can be studied from these plots: What are your findings? b. Prepare a normal Q-Q plot of the residuals. Does the normality assumption appear to be reasonable here? c. The observations within each factor level are in time order. Prepare residual sequence plots and analyze them. What are your findings? d. Obtain the studentized deleted residuals. Solution:
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In this plot, all 3 treatments have about the same extent of dispersion of the residuals around 0. Thus, the error variances are about equal across these treatments. b. The normal Q-Q plot on combined residuals across all 3 treatments is shown below:
c. The residual sequence plots are shown below: 2
18.15 Helicopter service. An operations analyst in a sheri ff ’s department studied how frequently their emer- gency helicopter was used during the past year, by time of day (shift 1: 2 A.M.- 8 A.M.; shift 2: 8 A.M.-2 P.M.; shift 3: 2 P.M.-8 P.M.; shirt 4: 8 P.M.-2 A.M.). Random samples of size 20 for each shift were obtained. The data are saved in “data 18.15.txt” (in time order). Since the data are counts, the analyst was concerned about the normality and equal variances assump-

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