EXAMPLE: from SmartPsych (today s assigned reading)

Transcription

1 Psychology 209 Single Factor Designs EXAMPLE: from SmartPsych (today s assigned reading) BPD clients present symptoms that include repeated suicidal behavior, self-mutilation, intense anger, and unstable interpersonal relationships. BPD clients are difficult to treat and few treatments have proved effective. Dr. Linehan and her collaborators have proposed a new therapy that is a combination of balancing client acceptance and encouraging behavior change. To test the effectiveness of this therapy, a study was conducted among women with BPD, ages Ps who were diagnosed with BPD were randomly assigned to two conditions: a year of new therapy versus old therapy. Each P s behavior was measured 4 times over 12 months. The measured behavior was suicidal behavior, use of emergency psychiatric services, and participation in treatment. New Treatment Ps showed statistically significantly less suicidal behavior, less use of psychiatric services, and greater participation in treatment than Old Treatment Ps.

2 1. What type of experimental design did the researchers use? Between- or Within-subject design? 2. How many factors (IVs)? How many levels are there of the factor (IV)? 3. How many conditions are there? How many participants in each condition? 4. What are the DVs? (3 of them) 5. Based on the statistical results, which treatment was more effective in treating BPD clients? 6. Internal validity concern: Suppose 20 of 22 Old Treatment Ps finished the study, but only 12 of 22 New Treatment Ps finished the study. How could attrition (a serious problem in year-long studies) influence the interpretation of results? 7. External validity concern: Can the results of this study be generalized to all people who are chronically suicidal? 8. Is this a true experiment? 9. Can the researcher claim cause (i.e., New Treatment caused the differences in outcomes)?

3 IV between-subjects or within-subjects? Between IV manipulated or subject variable? Within IV is manipulated Manipulated Subject Forming equivalent groups by Groups intrinsically not equal How often tested per condition? Random assignment Matching Possible matching to reduce nonequivalence Once > Once Full/partial counterbalance Reverse/block counterbalance Independent groups (insecurity study) Matched groups (sleep deprivation study) Nonequivalent groups (brain injury study) Repeated measures design (infant optic flow)

4 Question: Does focusing on your future death make you more insecure (materialistic)? Summary: Ps were randomly assigned to either death or music groups ( Write an essay on the feelings and thoughts concerning ). After a filler task, Ps were asked, Think of your life 15 years from now. How much is your future income? How much do you spend per year on travel? Ps who thought of death reported greater future income and money spent on travel than those who thought of music. What is the IV? The DVs? What is the null hypothesis? What is the alternative hypothesis? Is the IV manipulated or subject selected? How do you form equivalent groups? What kind of single-factor experimental design is this study? Answer: Independent groups design

5 Question: Does sleep deprivation make people more susceptible to leading questions in interrogation? Summary: Participants who slept roughly 8.5 hours a night were recruited for a study. They were randomly assigned to either a sleep deprivation or regular sleep groups. Ps assigned to the sleep deprivation group were kept awake for 21 hours straight. Ps assigned to the regular sleep group were allowed to sleep as usual. After sleep (deprivation or regular), Ps listened to a story and responded to misleading questions that could not be answered based on the story. After responding, Ps were given negative feedback and then questioned again to see if their answers changed. Ps who were sleep-deprived changed their answers more than Ps who had regular amounts of sleep. To make sure that the results were not due to individual differences in normal sleep patterns, the researchers asked the Ps to report how many hours they normally sleep per night (not in the study). Ps assigned to the regular sleep group reported an average of 8.5 hours per night. Ps assigned to the deprived sleep group reported an average of 8.4 hours per night. The researchers concluded that the groups were equivalent except for the condition they were placed in the study. What is the IV? The DVs? What is the null hypothesis? What is the alternative hypothesis? Is the IV manipulated or subject selected? How do you form equivalent groups? What kind of single-factor experimental design is this study? Answer: Matched groups design

6 Question: Do people with traumatic brain injuries have more difficult in interpreting emotions in other people than people without brain injuries? Summary: Ps with brain injuries and Ps without brain injuries watched videos with people who were displaying sarcasm, people who were lying to another person, and people who were sincere. Ps were the same gender and age, and had the same levels of education. Ps were asked to identify which videos represented sarcasm versus lying, and which represented sincerity versus sarcasm. Ps with brain injuries were less able to make correct distinctions compared with Ps without brain injuries. What is the IV? The DVs? What is the null hypothesis? What is the alternative hypothesis? Is the IV manipulated or subject selected? How do you form equivalent groups? What kind of single-factor experimental design is this study? Answer: Non-equivalent groups design