Answers on page 525. 17.6 Return to the study first described in Question 16.5 o

Question

Answers on page 525. 17.6 Return to the study first described in Question 16.5 on page 336, where a psychologist tests whether shy college students initiate more eye con with strangers because of training sessions in assertive behavior. Use data, but now assume that eight subjects, coded as A, B,... G, H, are repeatedly after zere. one, two, and three training sessions. (Inci- dentally, since the psychologist is interested in any learning or sequential effect, it would not make sense--indeed, it's impossible, given the sequen- ial nature of the independent variable-to counterbalance the four ses- sions.) The results are expressed as the observed number of eye contacts: Copyright 2015 3ohn Wiley & Sons, Inc. 401 REVIEW QUESTIONS

Explanation / Answer

x=c(1,2,4,7,0,1,2,6,0,2,3,6,2,4,6,7,3,4,7,9,4,6,8,10,2,3,5,8,1,3,5,7)
Session=c(rep("S0",8), rep("S1",8), rep("S2",8),rep("S3",8))
y=data.frame(x,Session)
results=aov(x~Session, data=y)
summary(results)

            Df Sum Sq Mean Sq F value Pr(>F)
Session      3 53.12 17.708   2.854 0.0551 .
Residuals   28 173.75   6.205               
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Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

TukeyHSD(results, conf.level = 0.95)

Tukey multiple comparisons of means
    95% family-wise confidence level

Fit: aov(formula = x ~ Session, data = y)

$Session
        diff         lwr      upr     p adj
S1-S0 0.875 -2.52567874 4.275679 0.8952244
S2-S0 3.500 0.09932126 6.900679 0.0418890
S3-S0 1.375 -2.02567874 4.775679 0.6900994
S2-S1 2.625 -0.77567874 6.025679 0.1754115
S3-S1 0.500 -2.90067874 3.900679 0.9776774
S3-S2 -2.125 -5.52567874 1.275679 0.3395416

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