Research Methods and Design I – Group Assignment #11 – How Fast?
Instructions: In 1974, Loftus and Palmer conducted a classic study demonstrating how the language used to ask a question can influence eyewitness memory. In the study, college students watched a film of an automobile accident and then were asked questions about what they saw. One group was asked, “About how fast were the cars 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 “smashed into” group reported significantly higher estimates of speed than the “hit” group. You, as a researcher wonder if Loftus and Palmer’s study is reliable, and repeats this study with a sample of students and obtains the following data.
|Hit Group||Smashed Into Group|
Your job is to determine if smashed into group reports higher speed than hit group. As you work on this problem, make sure to provide information for each of the eight steps we cover in Chapter 11 (Salkind) as well as the APA write-up you would see in a results section.
- State the null and alternative hypotheses
- Tell me your level of risk
- Determine the best statistical test to use
- Compute the test statistic. (Note: You can use the table below to help you calculate your SD, which will be important later when you write up your means and SDs)!
|Hit||X – M||(X – M)2||Smashed Into||X – M||(X – M)2|
|n – 1|
|(X – M)2 / n – 1|
|SD (√ )|
- Determine the value needed to reject the null hypothesis. Remember to calculate the correct degrees of freedom before finding the critical t-value! Note whether it is best to use the one-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 results section of an empirical research paper. Make sure to include the means and SDs for smashed into and hit group (in miles). I do NOT need to see the effect size (Cohen’s D)
- Was your obtained t-value positive or negative? Would it matter either way? With your discussion group, tell my why a positive or negative value is not important when it comes to your obtained value
- What is more appropriate to use for your data set: the one-tailed t-Test or the two-tailed t-Test. Why?
- Why would it be easier to find significance using a p value of .05 than a p value of .01?
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