PYSC 224 Introduction to Experimental Psychology

Transcription

1 PYSC 224 Introduction to Experimental Psychology Session 5 True Experimental Designs- Part 2 Lecturer: Dr. Margaret Amankwah-Poku, Dept. of Psychology Contact Information: mamankwah-poku@ug.edu.gh College of Education School of Continuing and Distance Education 2015/ /2017

2 Session Overview As indicated in the previous session betweenparticipant posttest only designs are used when different participants are tested in each experimental condition Typically, there are three main types of between-participant posttest only designs On the other hand is the within-participant posttest only design which is also known as the repeated measures design Dr. Margaret Amankwah-Poku Slide 2

3 Session Goals and Objectives At the end of the session, you should be able to Determine when to use these types of betweenparticipant posttest-only designs Use practical examples to explain these designs Discuss the within-subject design and how it differs from the between participant design Describe the within-participant design Dr. Margaret Amankwah-Poku Slide 3

4 Session Outline The key topics to be covered in the session are as follows: Between-participants posttest only designs Within-participant posttest-only Design Dr. Margaret Amankwah-Poku Slide 4

5 Reading List Christensen, B.L. (2007). Experimental Methodology (10th ed.). Boston: Allyn & Bacon. (p ) Kantowitz, B. H., Roediger III, H. L., Elmes, D. G. (2015). Experimental Psychology. Stamford: Cengage Learning (Pp 74) Martin, D. W. (2008). Doing Psychology Experiments. Belmont, CA: Thomson Higher Education (p ) Dr. Margaret Amankwah-Poku Slide 5

6 Topic One BETWEEN-PARTICIPANTS POSTTEST ONLY DESIGN Dr. Margaret Amankwah-Poku Slide 6

7 2. Posttest-only design Recap from Session 5 Part 1 a. Between-participants design Three main types will be discussed a. Two group between participant design b. Simple randomized participants design c. Factorial design b. Within-participants design Dr. Margaret Amankwah-Poku Slide 7

8 a. Between-participant Posttest- Only Design Types of between-participants designs i. Two group between participant design ii. Simple randomized design/ random participants design iii. Factorial design Dr. Margaret Amankwah-Poku Slide 8

9 i. Two group between-participant posttest-only design Two groups of participants are tested- an experimental and a control group The independent variable is administered to only the experimental group Then the dependent variable is measured in both groups and compared to assess the influence of the independent variable This is the same as the basic posttest only design Dr. Margaret Amankwah-Poku Slide 9

10 i. Two group between participant design Participants R Experimental Group Administer Independent Variable Measure Dependent Variable R Control Group No Independent Variable Measure Dependent Variable Dr. Margaret Amankwah-Poku Slide 10

11 ii. Simple randomized participants design The influence of several levels of variation of the independent variable is investigated The two group between-participant design is extended to include more than one level of the independent variable Thus, varying amounts of an independent variable is given to different groups of participants There is random assignment of participants Dr. Margaret Amankwah-Poku Slide 11

12 ii. Simple randomized participants design Example- the effect of exercise on weight lose A single independent variable with more than 2 levels Three (3) different experimental groups receiving different levels of exercise and one control group Dr. Margaret Amankwah-Poku Slide 12

13 ii. Simple randomized participants design Example 1 Exptal Grp 1 20 mins. Exptal Grp 2 40 mins. Exptal Grp 3 60 mins. Control Grp 0 min. Dr. Margaret Amankwah-Poku Slide 13

14 ii. Simple randomized participants design Effect of feedback on performance Group 1 Group 2 Group 3 Group 4 No Feedback Negative feedback Positive Feedback Sandwich Feedback Dr. Margaret Amankwah-Poku Slide 14

15 iii. Factorial Design Sometimes psychological process may have several causes that interact with each other Factorial design- a researcher studies two or more independent variables together at a time Then, determine their independent and interactive effect Thus, several hypotheses can be test at the same time Dr. Margaret Amankwah-Poku Slide 15

16 iii. Factorial Design Example- The effect of diet and exercise on weight loss The effect of feedback and practice on performance The effect of Intelligence Quotient (I.Q.) and test anxiety on test performance All of the possible combinations of selected values of each variable can be tested Dr. Margaret Amankwah-Poku Slide 16

17 iii. Factorial Design Exercise Diet Walking Aerobics Combination (W & A) Normal NW NA NC Healthy HW HA HC Dr. Margaret Amankwah-Poku Slide 17

18 iii. Factorial Design Feedback Practice Positive Negative Sandwich FB Short (10m) SP SN SS Mod (20m) MP MN SS Long (30m) LP LN HC Dr. Margaret Amankwah-Poku Slide 18

19 iii. Factorial Design Example- The effect of Belief and Food type on emotional response Beliefs = 2 levels Food type = 3 levels Dr. Margaret Amankwah-Poku Slide 19

20 iii. Factorial Design Dr. Margaret Amankwah-Poku Slide 20

21 iii. Factorial Design Food type Food Belief High Fat Savoury High Fat Sweet Low Calorie Rational R-HFSV R-HFSW R-LC Irrational IR-HFSV IR-HFSV IR-LC Dr. Margaret Amankwah-Poku Slide 21

22 iii. Factorial Design Types of factorial design 1. Between participant factorial design 2. Within participant factorial design 3. Mixed factorial design Dr. Margaret Amankwah-Poku Slide 22

23 iii. Factorial Design In a factorial design, two effects are investigated Main effect Interaction effect 1. Main effect- the influence of one independent variable on the dependent variable Dr. Margaret Amankwah-Poku Slide 23

24 iii. Factorial Design Exercise Diet Walking Aerobics Combination (W & A) Normal NW NA NC Healthy HW HA HC Dr. Margaret Amankwah-Poku Slide 24

25 iii. Factorial Design 1. Main Effect Example- the effect of belief alone or food alone on emotional response Effect of the following on emotional response Rational and irrational belief High fat savoury, high fat sweet, and low calorie Effect of the following on weight Normal and healthy diet Walking, aerobics and combination Dr. Margaret Amankwah-Poku Slide 25

26 iii. Factorial Design 2. Interaction effect- the different variable Example- levels of the two independent variables interacting to affect the dependent How will eating a normal or healthy diet combined with the various forms of exercise, to affect weight lose etc. E.g.- Healthy diet and aerobics Thus, 6 possible combinations/ interaction effects of the two independent variables can be tested Dr. Margaret Amankwah-Poku Slide 26

27 iii. Factorial Design Exercise Diet Walking Aerobics Combination (W & A) Normal NW NA NC Healthy HW HA HC Dr. Margaret Amankwah-Poku Slide 27

28 iii. Factorial Design Advantages of the factorial design The experimenter can examine more than one hypothesis at the same time Interactive effects can be studied Economical- in terms of the number of participants to be tested and the amount of effort that the experimenter would expend The researcher can control variable that are potentially confounding Dr. Margaret Amankwah-Poku Slide 28

29 iii. Factorial Design Disadvantage of the factorial design Where there is an interactional effect (3 IVs) the experimenter will have to perform further analysis to determine where the difference lies *Read more about this Dr. Margaret Amankwah-Poku Slide 29

30 Topic Two WITHIN-PARTICIPANT POSTTEST- ONLY DESIGN Dr. Margaret Amankwah-Poku Slide 30

31 b. Within-participant Posttest-only Design The same participants take part in all the experimental conditions They are assessed repeatedly on the dependent variable in all the treatment groups Also called the repeated measures design, because the same participants are measured repeatedly Dr. Margaret Amankwah-Poku Slide 31

32 b. Within-participant Posttest-only Design Example- Effect of food type on emotional response or Effect of belief on emotional response The experimenter will have only 1 group of participants Only one group will be primed with both rational and irrational beliefs Or only one group will view the three food types Dr. Margaret Amankwah-Poku Slide 32

33 b. Within-participant Posttest-only Design Participants Food type 1 Food type 2 Food type3 P1 HFSAV HFSW LC P2 HFSAV HFSW LC P3 HFSAV HFSW LC P4 HFSAV HFSW LC P5 HFSAV HFSW LC.P36 HFSAV HFSW LC Dr. Margaret Amankwah-Poku Slide 33

34 b. Within-participant Posttestonly Design Participants Rational Irrational P1 Rational Irrational P2 Rational Irrational P3 Rational Irrational P4 Rational Irrational P5 Rational Irrational.P36 Rational Irrational Dr. Margaret Amankwah-Poku Slide 34

35 b. Within-participant Posttest-only Design Participants Walking Aerobics Combination P1 Walking Aerobics Combination P2 Walking Aerobics Combination P3 Walking Aerobics Combination P4 Walking Aerobics Combination P5 Walking Aerobics Combination.P36 Walking Aerobics Combination Dr. Margaret Amankwah-Poku Slide 35

36 b. Within-participant Posttest only Design Advantage of Within-participant design The researcher need not worry about creating equivalence among the participants- same participants are tested in all the treatment conditions Fewer participants are needed because the same participants are tested repeatedly Dr. Margaret Amankwah-Poku Slide 36

37 b. Within-participant Posttest only Design Disadvantage of Within-participant design 1. Major problem- Sequencing effect as a result of the different conditions presented in a particular sequence Sequencing effect is made up of 1. Order effect 2. Carryover effect Dr. Margaret Amankwah-Poku Slide 37

38 b. Within-participant Posttest only Design Examples of order effects associated with the passage of time: a. practice effect- an improvement in performance as a result of repeated practice with a task b. fatigue effect- a deterioration in performance as participants become bored, tired or distracted Dr. Margaret Amankwah-Poku Slide 38

39 b. Within-participant Posttest only Design Carryover effect- occurs when a particular treatment changes the behaviour observed in the subsequent treatment The previous treatment has an effect on the participants and this effect is carried over into the next treatment Example- Experiment involving the administration of alcohol Dr. Margaret Amankwah-Poku Slide 39

40 b. Within-participant Posttest only Design 2. Within-participant design is more demanding on the participants as they may become tired or bored 3. It may be difficult to find participants who are willing to take part Dr. Margaret Amankwah-Poku Slide 40

41 END OF SESSION 5 Part 2

42 References Christensen, B.L. (2007). Experimental Methodology (10th ed.). Boston: Allyn & Bacon. (p , , ) Dr. Margaret Amankwah-Poku Slide 42