Exam 3

20. (8` points) Two observers observe a child in the classroom every 30 minutes to record whether he is behaving aggressively. They use two categories for their observations: yes (aggressive) or no (not aggressive). Using the data presented below, answer the following question.   

Calculate and report the observers' interobserver reliability. 

Do you think the observers demonstrated acceptable interobserver reliability? Why or why not?

21. (5 points) A researcher was interested in determining whether more frequent breaks (i.e., "coffee breaks") in a business setting would help employees to be more productive. With the cooperation of the management, employees on one floor of the corporate offices were allowed to take a 10-minute break each hour (at any time) between 8:00 and 11:00 A.M. (for a total of 30 minutes). The comparison group comprised employees on different floors who followed the usual corporate policy of taking a 30-minute break sometime during the morning (at any time). Measures of productivity were gathered for each employee according to his or her job (e.g., number of reports written, number of sales made, etc.). A time series analysis was applied to compare the productivity of both groups of employees for six months before and after the intervention (started in July). Quite surprisingly, the productivity of both groups increased following the onset of the intervention, suggesting to the researcher that the timing of breaks makes no difference.

What type of research design was used in this study? 

Describe two ways in which contamination may have influenced the results of this study. 

Describe one threat to internal validity that might be present in this study because the independent variable manipulation was implemented on different floors of the building.