Are Students Overly Optimistic About Time Requirements? People tend to be overly optimistic about many things including income, debt, grades, illness, and marriage (e.g., Shepperd et al., 2015; Weinstein, 1980). People also exhibit unrealistic optimism when estimating how long tasks will take to complete, called the planning fallacy (e.g., Buehler et al., 1994; Kahneman & Tversky, 1979). When students habitually commit the planning fallacy, it can leave them insufficient time for important tasks. The planning fallacy may explain why individuals do not perform optimally in school and/or at work. Do statistics students exhibit the planning fallacy? Can they accurately predict the time required to complete a practice test for a statistics course? You recruit a representative sample of 103 stu- dents in a statistics course at your university and ask them to estimate how many minutes it will take them to complete the test. This is the third practice test of the semester so the students have experience completing this sort of task. After making their predictions, students complete the practice test online and each student's completion time is recorded to the nearest minute. You compute the difference between each student's predicted time and the actual completion time (predicted-actual). A negative difference indicates a student underestimated, a positive difference indicates a student overestimated, and a zero would be a perfect prediction. Based on previous research on unrealistic optimism, you expect students will underesti- mate the task time. However, you recognize that both underestimation and overestima- tion have important implications for statistics students. You need to consider this when you determine if a one- or two-tailed hypothesis test is appropriate. The data file is on the textbook website. Pillar 1: Null Hypothesis Testing With a Continuous p Value Step 1: Choose the Correct Test Statistic 1. Why is a single sample & test the correct statistic for this research scenario? a. You are comparing one sample mean to a known test value (0). b. You are comparing a sample mean to a different sample mean.168 Part 2 . Applying the Four Pillars of Scientific Reasoning to Mean Differences 2. In this research situation, is a one- or two-tailed hypothesis test appropriate? A one-tailed test is appropriate. You expect students to underestimate the time it takes to complete the practice statistics exam and results in the opposite direction would not be interesting. b. A two-tailed test is appropriate. Both underestimation and overestimation have important implications for statistics students. Step 2: Examine Statistical Assumptions 3. All the necessary assumptions are met by this study. Match each of the statistical assumptions to the fact that implies the assumption was met. Independence Appropriate measurement of the IV and DV Normality Homogeneity of variance a. It is unlikely that the SD and or will be dramatically different. b. The DV is measured on an interval ratio scale. c. The population of scores has a normal shape. d. The scores from each participant were collected so one participant's scores did not affect anyone else's scores. Step 3: Identify the Statistical Null Hypothesis The data file has the difference scores for each participant computed as (predicted time - actual time = time difference). Therefore, if students are overly optimistic in their time estimates, the time difference would be_ _(positive/ negative) 5. Choose the correct statistical null hypothesis. 2. H, =0 b. H = M