Question

Loftus and Palmer study (1974) demonstrated the influence of language on eyewitness memory. Participants watched a film of a car accident and were asked questions about what they saw. One group was asked “About how fast the cars were going when they smashed into each other?” Another group was asked the same question, except the verb was changed to “hit” instead of “smashed into”. The ‘smasher into” group reported significantly higher estimates of speed than the hit group. Suppose a researcher repeats this study with two samples of college students and obtains the following results:

Estimated Speed
Smashed into	hit
n = 15	n = 15
M = 40.8	M = 34.0
SS = 510	SS = 414

Is there a significantly higher estimated speed for the “smashed into” group? Use a one-tailed test with α = .01.

a)The critical t value is

(Note: leave the 4 decimal places after the decimal point)

b)Use the data to make a 99% confidence interval estimate of the mean difference in estimate speed between the “smashed into” group and the “hit” group

The lower limit of the confidence interval is:

c)Use the data to make a 99% confidence interval estimate of the mean difference in estimate speed between the “smashed into” group and the “hit” group

The upper limit of the confidence interval is:

Answer 1

a)The critical t value is

2.4671

(Note: leave the 4 decimal places after the decimal point)

b)Use the data to make a 99% confidence interval estimate of the mean difference in estimate speed between the “smashed into” group and the “hit” group

The lower limit of the confidence interval is:

-14.8876

c)Use the data to make a 99% confidence interval estimate of the mean difference in estimate speed between the “smashed into” group and the “hit” group

The upper limit of the confidence interval is:

28.4876

The output is:

1	2
40.8	34	mean
22.58317958	20.34698995	std. dev.
15	15	n
	28	df
	6.8000	difference (1 - 2)
	462.0000	pooled variance
	21.4942	pooled std. dev.
	7.8486	standard error of difference
	-14.8876	confidence interval 99.% lower
	28.4876	confidence interval 99.% upper
	21.6876	margin of error