Year of Class % of Students Completing Homework Average on Midterm 2000 50 76 2001 43 70 2002 60 81 2003 65 84 2004 52 72 2005 80 93 2006 61 83 2007 35 70 2008 75 89     This is an example of a  Case series Cross sectional study Correlational study None of the above   Describe the results of this study.    In general, what are the limitations of this type of study.      What are the particular limitations of this study?

Interaction a. What is an interaction between two factors? b. In general, when using two-way analysis of variance, if we find that there is an interaction effect, how does that affect the procedure? c. Shown below is an interaction graph constructed from the data in Exercise 1. What does the graph suggest?

Discussion Question: In this research study, one group was asked to watch a car accident and were asked to estimate the speed of the car after it "hit" the other car, while a different group also watched an accident but instead were asked to estimate the speed after the cars "collided." Explain why an independent samples t-test was used, and give your own example of a research study in which an independent samples t-test would be the appropriate statistical analysis.

Age discrimination: The following table presents the numbers of employees, by age group, who were promoted, or not promoted, in a sample drawn from a certain industry during the past year. Age Under 30 30-39 40-49 50 and Over MT 23 23 29 47 Promoted Not promoted Send data to Excel 11 39 6 37 Can you conclude that the people in some age groups are more likely to be promoted than those in other age groups? Use Excel and the a=0.01 level of significance. We (Choose one) the null hypothesis. There (Choose one) enough evidence at the a=0.01 level of significance to say that people in some age groups are more likely to be promoted. X