When researchers discuss statistical interaction, what type of variable are researchers focusing on?

Extra Credit – No Penalty for Trying If a researcher has a nominal/categorical variable like Sport Participated In (Swimming, Basketball, Track, Soccer), what is meant when a researcher creates “dummy variables” to represent this variable?  What is a dummy variable?

Power can range from -1 to +1.

A researcher was interested in comparing 3 group conditions: Meditation, Progressive Muscle Relaxation PMR), and a Control condition on heart rate. 28 freshmen undergraduates from USF were randomly selected.  From these 28 students, 13 were randomized to the Control Condition, 8 were randomly assigned to Meditation, and 7 were randomly assigned to Progressive Muscle Relaxation. Using a .05 level of significance is there a statistically significant difference between PMR and Meditation?

A researcher examined the body mass index (BMI) of 1000 randomly selected undergraduates from USF and found a mean of 25. If the median BMI was 18, what would you conclude about the shape of the distribution of BMI scores?

A researcher measured body mass (BM) for 100 undergraduates. The mean BM was 20 (SD=4). What would a person’s z-score be if the person had a body mass of 12?

Extra Credit – No Penalty for Trying Suppose a researcher compares 4 groups (Freshmen, Sophomores, Juniors, Seniors) on the average number of steps taken per day, and finds an overall significant F-ratio. What is the logic of using post hoc methods like the Tukey method or Bonferroni method in making pairwise comparisons (why are these special methods needed)?

A researcher was interested in comparing 3 group conditions: Meditation, Progressive Relaxation, and a Control condition on heart rate. 28 freshmen undergraduates from USF were randomly selected.  From these 28 students, 13 were randomized to the Control Condition, 8 were randomly assigned to Meditation, and 7 were randomly assigned to Progressive Relaxation. What statistical technique would be used in this study?

A researcher was interested in comparing 3 group conditions: Meditation, Progressive Relaxation, and a Control condition on heart rate. 28 freshmen undergraduates from USF were randomly selected.  From these 28 students, 13 were randomized to the Control Condition, 8 were randomly assigned to Meditation, and 7 were randomly assigned to Progressive Relaxation. What would be the degrees of freedom for: Between groups df = _____  

For an independent samples t-test, list the 3 assumptions underlying the statistical test.