Owens et al. (2010) wanted to investigate the impact of school start time on the sleep patterns of adolescents. They studied teenagers who were enrolled in high school, both before (fall semester) and after (spring semester) the entire school had decided to shift its start time from 8:00 a.m. to 8:30 a.m. Students completed a survey asking what time they went to bed the night before, how many hours of sleep they'd gotten, and their daytime sleepiness and level of depressed mood. The researchers found that after the 8:30 a.m. start time was implemented, students reported getting 45 minutes more sleep each night, and the percentage of student who reported more than 8 hours per night jumped from 16.4% to 54.7%. In addition, students' level of daytime sleepiness and depressed mood decreased after the 8:30 start time began.

1. Identify the independent and dependent variables.

• IV: Shift of start time
• DV: Students sleepiness, level of depressed mood, time they went to bed, the amount of sleep they got

(this question is done)

2. What causal statement might the researchers be trying to make, if any? Is it appropriate? Use the result and design to evaluate the study's internal validity.

• The causal statement the researchers might be trying to make is that starting school early indicates higher levels of sleepiness and depressed moods among highschoolers. It may not be appropriate because the percentages increased, and students had more sleep.

(this question is done)

3. If you notice any internal validity flows, can you redesign the study to remove the flow?

There are no internal validity flows.