Announcements: Exam 2 grades posted this afternoon Mean = 41.57; Median = 43; Mode = 47

Transcription

1 Announcements: Exam 2 grades posted this afternoon Mean = 41.57; Median = 43; Mode = 47 Histogram Frequency EC: mean = 4.11; median = 5; mode = 5 Mean =41.57 Std. Dev. =5.81 N =187 Histogram Frequency Factorial Designs: Mean =4.11 Std. Dev. =1.164 N =187

2 1. In single factor designs (only one factor), the IV must be either a between-subjects or a within-subjects variable. 2. In factorial designs (more than one factor), you can have both types of variables in the design P refers to person or subject variable IV, implies a betweensubjects variable E refers to manipulated IV (manipulated environment) Mixed refers to using both between-subjects and withinsubjects variables (default is between-subjects only) P X E Factorial Design: All IVS are between-subjects, but at least one IV is manipulated (Environment or E), and at least one IV is a subject variable (Person or P). Mixed P X E Factorial Design: At least one IV is betweensubjects (subject variable or P), at least one IV is within-subjects (manipulated variable or E). Mixed (E X E) Factorial Design: At least one IV is betweensubjects (manipulated variable or E), at least one IV is withinsubjects (manipulated variable or E)

3 Between-subjects variables: Need to create equivalent (random assignment, matching) Within-subjects variables: Potential sequence effects (counterbalancing) In P X E: worry about creating equivalent In Mixed P X E: worry about creating equivalent and potential sequence effects In Mixed Factorial Designs (E X E): worry about creating equivalent and potential sequence effects

4 EXAMPLE: Killer whales A researcher is interested in studying the effects of vessel noise on the echolocation abilities of killer whales. She goes to Sea World and designs an experiment to test the hypothesis that vessel noise masks echolocation noises, rendering the killer whales unable to locate fish. Using a tape recorder and speaker, she pipes vessel noise into the tank where the whales are located, and then releases fish into the tank. She measures how long it takes each killer whale to find 10 fish with and without the vessel noise. Each whale is tested separately in the tank, and the fish are released one at a time (5 fish released with vessel noise, 5 fish released without vessel noise). She uses 3 male and 3 female killer whales for her experiment, and the ages of the whales range from 2 to 15. Echolocation abilities deteriorate with age. However, echolocation abilities do not differ in males and females. The researcher includes both sexes because these whales are available as subjects; she is not interested in studying sex differences. Whale 1 Whale 2 Whale 3 Whale 4 Whale 5 Whale 6 Vessel Noise No Yes No Yes No Yes No Yes No Yes 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish

5 What kind of a design is this? IV = vessel noise (within-subject manipulated) Single factor, within-subjects design = repeated measures factorial Vessel Noise No Yes Mean # Fish (1-5) n=6 Mean # Fish (1-5) n=6

6 Let s change the study: P X E DESIGN A researcher is interested in studying the effects of vessel noise on the echolocation abilities of killer whales and potential sex differences in these effects. She goes to Sea World and designs an experiment to test the hypothesis that vessel noise masks echolocation noises, rendering the killer whales unable to locate fish. Using a tape recorder and speaker, she pipes vessel noise into the tank where the whales are located, and then releases fish into the tank. She uses 4 male and 4 female killer whales for her experiment. The killer whales are matched by gender and assigned to a condition where fish are released with vessel noise or without vessel noise. She measures how long it takes each killer whale to find 10 fish, released individually (10 fish with vessel noise or 10 fish without vessel noise). Vessel Noise N Y N Y N Y N Y N Y N Y N Y N Y N Y N Y F F F F M M M M

7 IV 1 = vessel noise (between-subject manipulated) IV 2 = gender (between-subject subject variable ) Multiple factors: between-subject (IV 1) and between subject (IV 2) = P X E Factorial (new!) Sex Female Mean # Fish (1-10) n=2 Male Mean # Fish (1-10) n=2 Vessel Noise No Yes Mean # Fish (1-10) n=2 Mean # Fish (1-10) n=2

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

9 Let s change the study again: MIXED P X E FACTORIAL A researcher is interested in studying the effects of vessel noise on the echolocation abilities of killer whales and potential sex differences in these effects. She goes to Sea World and designs an experiment to test the hypothesis that vessel noise masks echolocation noises, rendering the killer whales unable to locate fish. Using a tape recorder and speaker, she pipes vessel noise into the tank where the whales are located, and then releases fish into the tank. She uses 4 male and 4 female killer whales for her experiment. The killer whales are matched by gender and assigned to a condition where fish are released with vessel noise AND without vessel noise. She measures how long it takes each killer whale to find 10 fish, released individually (5 fish with vessel noise or 5 fish without vessel noise). Vessel Noise No Yes No Yes No Yes No Yes No Yes F1 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish F2 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish F3 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish F4 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish M1 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish M2 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish M3 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish M4 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish 1 Fish

10 IV 1 = vessel noise (within-subject manipulated) IV 2 = gender (between-subject subject variable ) Multiple factors: within-subject (IV 1) and between subject (IV 2) = Mixed P X E Factorial Sex Female Mean # Fish (1-5) n=4 Male Mean # Fish (1-5) n=4 Vessel Noise No Yes Mean # Fish (1-5) n=4 Mean # Fish (1-5) n=4

11 IV between-subjects or within-subjects? ALL Between IV manipulated or subject variable? At least 1 between, at least 1 within ALL Within IV is manipulated Manipulated Subject Between= Subject variable Forming equivalent by Groups intrinsically not equal How often tested per condition? Random assignment Matching Possible matching to reduce nonequivalence Once > Once Independent (insecurity Matched (sleep deprivation Nonequivalent (brain injury Mixed P X E Factorial Full/partial counterbalance Reverse/block counterbalance Repeated measures design (infant optic flow)

12 Mixed Factorial: Spider and horror films Is it the spider that is scary or is the situation created in a horror film? IV1: low versus high self-efficacy (manipulated betweensubjects variable) IV2: approaching versus withdrawing spider (counterbalanced within-subjects variable) Self-efficacy Row Means High Low Spider Approaches Film Still/Avoids Column Means Looks like two main effects from the descriptive statistics (3.62>2.44, 3.57>2.49) Interaction? Let s graph the descriptives (not using inferential statistics)

13 Mixed Factorial: Spider Study 5 4 Fear Rating 3 2 High Low 1 0 Approaches Spider Film Still/Avoids Mixed Factorial: Spider Study Fear Rating 2 Approaches Still/Avoids 1 0 High Self-efficacy Low Fear Rating Approaches Still/Avoids High Self-efficacy Low

14 Interaction: A large amount of fear occurred when the situation of a bad horror movie was simulated (approaching spider plus low self-efficacy), while the film viewers reported only moderate to low amounts of fear in the other three conditions. Interpretation: For high self-efficacy participants, fear was fairly low regardless of the relative motion of the spider. On the other hand, for those experience low self-efficacy, the amount of fear was clearly affected by whether the spider was looming or not. (p. 290)

15 IV between-subjects or within-subjects? ALL Between IV manipulated or subject variable? At least 1 between, at least 1 within ALL Within IV is manipulated Manipulated Subject Between = Manipulated Forming equivalent by Groups intrinsically not equal How often tested per condition? Random assignment Matching Possible matching to reduce nonequivalence Once > Once Independent (insecurity Matched (sleep deprivation Nonequivalent (brain injury Mixed (E X E) Factorial Full/partial counterbalance Reverse/block counterbalance Repeated measures design (infant optic flow)