Quasi-Experimental and Single Subject (small N) Designs

1. Quasi-Experimental and Single Subject (small N) Designs Psychological Research Methods

2. Quasi-Experimental Designs Examples (Adapted from Salkind, 2000) • Differences in the personalities of abused versus non-abused children • Effect of malnutrition on infants • Effects of maternal cocaine use during pregnancy • Effects of pre-conception, paternal exposure to gametic mutagens • Differences in intellectual capacity between old people placed in nursing homes and those living at home

3. Quasi-Experimental Designs • Non-equivalent Groups

7. Quasi-Experimental Designs • Proxy Pretest • Separate Pretest and Posttest Groups

8. Differences between Experimental and Quasi-Experimental Designs

9. Differences between Experimental and Quasi-Experimental Designs

10. Differences between Experimental and Quasi-Experimental Designs

11. Differences between Experimental and Quasi-Experimental Designs

12. Differences between Experimental and Quasi-Experimental Designs

13. Single Subject (small N) Designs • Nomothetic Research • Idiographic Research

14. Single Subject (small N) Designs • Why use an N of 1?

15. Single Subject (small N) Designs • Procedures • Baseline Measure • Stability • Treatment Measure • Types • AB • ABA • ABC… • Multiple Baselines across Behaviors • Multiple Baselines across Subjects

16. Single Subject (small N) DesignsTypes – AB A 6-month old girl who was born with a cleft palate repeatedly engaged in forcing her tongue to the back of her mouth which resulted in vomiting. She did this behavior so frequently that she was severely underweight, dehydrated, and malnourished. Baseline observations indicated that she was engaging in this behavior 50% of the time while she was awake (Sajwaj et al., 1974).

17. Single Subject (small N) DesignsTypes – AB • The Intervention • The Result

18. Single Subject (small N) DesignsTypes – AB At age 4, a young boy began engaging in extreme hyperactivity, screaming, and self-injury. He went through years of psychotherapy and drug treatment, but nothing was successful. The self injury included head banging, slapping, and punching himself in the face. Baseline measurements indicated that he was engaging in approximately 400 self-injuries per hour. By the age of 9 he was nearly blind and was frequently tied to a bed to prevent further self-injury (Tate & Baroff, 1996).

19. Single Subject (small N) DesignsTypes – AB • The Intervention • The Result

20. Single Subject (small N) DesignsTypes – AB A 4-year-old boy was engaging in hyperactivity and destructive behaviors. He would smash things, knock over furniture, rip apart books, lick things, spit, scream, and conspicuously wet his pants. His behavior was destroying his family. Baseline observations indicated that 60% of the time he was engaging in these behaviors (Mace et al., 1986).

21. Single Subject (small N) DesignsTypes – AB • The Intervention • The Result

22. Single Subject (small N) DesignsTypes – ABA A 6-year-old autistic girl with an IQ of 20 was engaging in self-stimulation and destructive behaviors. The self-stimulation consisted of hand flapping, arching her back, and flapping toys in front of her eyes. She also threw toys and scrapped the walls and furniture. Baseline measurements indicated that she was doing this over 80% of the time (Charlop et al., 1988).

23. Single Subject (small N) DesignsTypes – ABA • The Intervention • The Result

24. Single Subject (small N) DesignsTypes – ABC An 8-year-old boy with an IQ of 27 attended special education classes. The boy would engage in hyperactivity behavior which included running around the class, yelling, throwing objects, and grabbing people. He engaged in these behaviors nearly 60% of the time (Foxx & Shapiro, 1978).

25. Single Subject (small N) DesignsTypes – ABC • The Intervention • The Result

26. Single Subject (small N) DesignsTypes – ABCD A mentally retarded man engaged in stereotypies and self-stimulation such as head weaving, repeated manipulation of objects, and rocking. These behaviors prevented normal functioning because they occurred almost 100% of the time that he was awake (Jordan et al., 1989).

27. Single Subject (small N) DesignsTypes – ABCD • The Intervention • The Result

28. Single Subject (small N) DesignsTypes – Multiple Baselines Across Behaviors BASELINE BASELINE & Tx Tx

29. Single Subject (small N) DesignsTypes – Multiple Baselines Across Subjects Baseline Baseline Baseline & Tx & Tx Tx

30. Single Subject (small N) DesignsWhat would you do? A 10-year-old boy averaged 63 violent outbursts per day in school. These outbursts included chocking, hitting, pulling and pushing others, as well as verbally abusing others. The outbursts occurred with such frequency and violence that the child had to be removed from the class for developmentally disabled children (Luce et al., 1980).

31. Single Subject (small N) DesignsWhat would you do? A 32-year old Deaf woman who has been diagnosed as profoundly retarded has been grinding her teeth together for the past 14 years. As a result, she has lost all but 5 of her upper teeth, and her lower teeth are severely worn away. Bruxism (teeth grinding) results in many problems. It destroys the teeth. It results in headaches, which make people irritable and unresponsive. Others find the noise aversive (Blount et al., 1982).

32. Single Subject (small N) DesignsWhat would you do? A 63-year-old woman diagnosed with undifferentiated schizophrenia was a 15 year resident of a psychiatric hospital. She repeatedly engaged in delusional verbal behavior. The content of the delusions was often graphically sexual (Ayllon & Houghton, 1964).

33. Single Subject (small N) DesignsWhat would you do? A 9-year-old girl who was diagnosed with mental retardation, cerebral palsy, aphasia, hyper-irritability, and brain damage would vomit repeatedly in class, often targeting the teacher and other students in the class. This was so disruptive that she could no longer attend the class. Repeated vomiting is harmful to the esophagus, digestive tract, teeth and stomach muscles. It also results in malnutrition (Wolf et al., 1965).