15. Problem 18 in Chapter 10 reported a research study in which eyewitness reports of an automobile accident were influenced by the language used to ask questions (Loftus

& Palmer, 1974). One group of n = 15 witnesses was asked how fast the cars were going when they “smashed into” each other and produced an average estimate of M = 40.8 mph with SS = 510. Another group of 15 witnesses was asked about the cars’ speed when they

“hit” each other and produced an average estimate of M = 34.0 mph with SS = 414.

a. Make a point estimate of the population mean difference in estimated speed.

b. Make an interval estimate of the population mean difference so that you are 95% confident that the true mean difference is in your interval.

c. Based on the confidence interval from part

b, are these data sufficient to conclude that there is a significant difference in estimated speed between the two conditions? Assume a two-tailed test with  = .05.