In 1974, Loftus and Palmer conducted a classic studydemonstrating how the language used to ask a question can influenceeyewitness memory. In the study, college students watched a film ofan automobile accident and then were asked questions about whatthey saw. One group was asked, “About how fast were the cars goingwhen they smashed into each other?†Another group was asked thesame question except the verb was changed to “hit†instead of“smashed into.†The “smashed into†group reported significantlyhigher estimates of speed than the “hit†group. You, as aresearcher wonder if Loftus and Palmer’s study is reliable, andrepeats this study with a sample of FIU students and obtains thefollowing data.
Hit Group | Smashed Into Group | |
32 | 50 | |
26 | 44 | |
40 | 54 | |
23 | 45 | |
42 | 44 | |
20 | 40 | |
37 | 49 | |
25 | 34 | |
24 | 38 | |
22 | 30 | |
19 | 50 | |
24 | 46 | |
19 | 40 | |
22 | 35 | |
29 | 43 | |
24 | 41 | |
34 | 30 | |
33 | 39 | |
37 | 44 | |
20 | 35 | |
Your job is to determine if smashed into group reports higherspeed than hit group. As you work on this problem, make sure toprovide information for each of the eight steps we cover in Chapter11 (Salkind) as well as the APA write-up you would see in a resultssection.
- State the null and alternative hypotheses
- Tell me your level of risk
- Determine the best statistical test to use
- Determine the value needed to reject the null hypothesis.Remember to calculate the correct degrees of freedom before findingthe critical t-value! Note whether it is best to use theone-tailed or two-tailed test.
- Compare the obtained and critical value
- Decide whether you will retain the null hypothesis or …
- Decide whether you will reject the null hypothesis
- Finally, write up your results as you would see it in a resultssection of an empirical research paper. Make sure to include themeans and SDs for smashed into and hit group (in miles). Ido NOT need to see the effect size (Cohen’s D)
- Was your obtained t-value positive or negative? Wouldit matter either way? With your discussion group, tell my why apositive or negative value is not important when it comes to yourobtained value
- What is more appropriate to use for your data set: theone-tailed t-Test or the two-tailed t-Test. Why?Would your APA write-up differ depending on which you used?
- Why would it be easier to find significance using a pvalue of .05 than a p value of .01?
- Finally (and this is the tough one), how would your resultshave differed with regard to steps 4 through 9 if you had usedn rather than n – 1?
