50.1K

Verified Solution

Link Copied!

Sigall and Ostrove(1975) did an experiment to assess whether the physicalattractiveness of a defendant on trial for a crime had an effect onthe severity of the sentence given in mock jury trials. Each of theparticipants in this study was randomly assigned to one of thefollowing three treatment groups; every participant received apacket that described a burglary and gave background informationabout the accused person. The three treatment groups differed inthe type of information they were given about the accused person’sappearance. Members of Group 1 were shown a photograph of anattractive person; members of Group 2 were shown a photograph of anunattractive person; members of Group 3 saw no photograph. Some oftheir results are described here. Each participant was asked toassign a sentence (in years) to the accused person; the researcherspredicted that more attractive persons would receive shortersentences.
	a.	Prior to assessment ofthe outcome, the researchers did a manipulation check. Members ofGroups 1 and 2 rated the attractiveness (on a 1 to 9 scale, with 9being the most attractive) of the person in the photo. Theyreported that for the attractive photo, M = 7.53; for theunattractive photo, M = 3.20, F(1, 108) = 184.29.Was this difference statistically significant (using α = .05)?
	b.	What was the effectsize for the difference in (2a)?
	c.	Was their attempt tomanipulate perceived attractiveness successful?
	d.	Why does the Fratio in (2a) have just df = 1 in the numerator?
	e.	The mean length ofsentence given in the three groups was as follows:
			Group 1: Attractive photo,M = 2.80
			Group 2: Unattractivephoto, M = 5.20
			Group 3: No photo,M = 5.10
		They did not report asingle overall F comparing all three groups; instead, theyreported selected pairwise comparisons. For Group 1 versus Group 2,F(1, 108) = 6.60, p < .025.     Was this difference statisticallysignificant? If they had done an overall F to assess thesignificance of differences of means among all three groups, do youthink this overall F would have been statisticallysignificant?
	f.	Was the difference inmean length of sentence in part (2e) in the predicteddirection?
	g.	Calculate and interpretan effect-size estimate for this obtained F.
	h.	What additionalinformation would you need about these data to do a Tukey honestlysignificant difference test to see whether Groups 2 and 3, as wellas 1 and 3, differed significantly?