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Stopped 24 147
by police
Not stopped 176 1253
by police
Minitab
Chi-Sq = 0.413, DF = 1, P-Value = 0.521
6. No Smoking The accompanying table summarizes successes and failures when sub-
jects used different methods in trying to stop smoking. The determination of smoking
or not smoking was made five months after the treatment was begun, and the data are
based on results from the Centers for Disease Control and Prevention. Use the
TI-83>84 Plus results (on the next page) with a 0.05 significance level to test the
claim that success is independent of the method used. If someone wants to stop smok-
ing, does the choice of the method make a difference?
Nicotine Gum Nicotine Patch
Smoking 191 263
Not smoking 59 57
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11-3 Contingency Tables: Independence and Homogeneity 617
TI-83/84 PLUS
7. Is the Vaccine Effective? In a USA Today article about an experimental vaccine for
children, the following statement was presented:  In a trial involving 1602 children,
only 14 (1%) of the 1070 who received the vaccine developed the flu, compared with
95 (18%) of the 532 who got a placebo. The data are shown in the table below. Use a
0.05 significance level to test for independence between the variable of treatment
(vaccine or placebo) and the variable representing flu (developed flu, did not develop
flu). Does the vaccine appear to be effective?
Developed Flu?
Yes No
Vaccine treatment 14 1056
Placebo 95 437
8. Pedestrian Fatalities A study was conducted of the association between intoxication
and pedestrian deaths, with the results shown in the accompanying table (based on
data from the National Highway Traffic Safety Administration). Use a 0.05 signifi-
cance level to test the claim that pedestrian fatalities are independent of the intoxica-
tion of the driver and the intoxication of the pedestrian.
Pedestrian Intoxicated Pedestrian Not Intoxicated
Driver intoxicated 59 79
Driver not intoxicated 266 581
9. Left-Handedness and Gender The table below is based on data from a Scripps Survey
Research Center poll. Use a 0.05 significance level to test the claim that gender and
left-handedness are independent.
Left-handed Not Left-handed
Male 83 17
Female 184 16
10. Birth Weight and Graduation The data in the table below are based on data from a
Time magazine article. Use a 0.05 significance level to test the claim that whether a
subject had low birth weight or normal birth weight is independent of whether the
subject graduates from high school by age 19. Do the results show that low birth
weight causes people to not graduate from high school by age 19?
Graduated from high school Did not graduate from high school
by age 19 by age 19
Low birth weight 8 42
Normal birth weight 86 64
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618 Chapter 11 Multinomial Experiments and Contingency Tables
11. Accuracy of Polygraph Tests The data in the accompanying table summarize results
from tests of the accuracy of polygraphs (based on data from the Office of Technol-
ogy Assessment). Use a 0.05 significance level to test the claim that whether the sub-
ject lies is independent of the polygraph indication. What do the results suggest about
the effectiveness of polygraphs?
Polygraph Indicated Polygraph Indicated
Truth Lie
Subject actually told the truth 65 15
Subject actually told a lie 3 17
12. Can Dogs Detect Cancer? An experiment was conducted to test the ability of dogs to
detect bladder cancer. Dogs were trained with urine samples from bladder cancer pa-
tients and people in a control group who did not have bladder cancer. Results are
given in the table below (based on data from the New York Times). Using a 0.01 sig-
nificance level, test the claim that the source of the sample (healthy or with bladder
cancer) is independent of the dog s selections. What do the results suggest about the
ability of dogs to detect bladder cancer? If the dogs did significantly better than ran-
dom guessing, did they do well enough to be used for accurate diagnoses?
Sample from subject Sample from subject
with bladder cancer without bladder cancer
Dog identified subject as cancerous 22 32
Dog did not identify subject as cancerous 32 282
13. Is Sentence Independent of Plea? Many people believe that criminals who plead
guilty tend to get lighter sentences than those who are convicted in trials. The ac-
companying table summarizes randomly selected sample data for San Francisco
defendants in burglary cases. All of the subjects had prior prison sentences. At the
0.05 significance level, test the claim that the sentence (sent to prison or not sent to
prison) is independent of the plea. If you were an attorney defending a guilty de-
fendant, would these results suggest that you should encourage a guilty plea?
Guilty Plea Not Guilty Plea
Sent to prison 392 58
Not sent to prison 564 14
Based on data from  Does It Pay to Plead Guilty? Differ-
ential Sentencing and the Functioning of the Criminal
Courts, by Brereton and Casper, Law and Society Review,
Vol. 16, No. 1.
14. Which Treatment Is Better? A randomized controlled trial was designed to compare
the effectiveness of splinting against surgery in the treatment of carpal tunnel syn-
drome. Results are given in the table below (based on data from  Splinting vs.
Surgery in the Treatment of Carpal Tunnel Syndrome, by Gerritsen et al., Journal of
the American Medical Association, Vol. 288, No. 10). The results are based on evalu- [ Pobierz całość w formacie PDF ]