PSYCH 312 1st Edition Exam # 3 Study Guide1. What do we mean when we say that control is the keystone to the experimental method?- Refers to design details used to ensure that results are due to IV and not other uncontrolled factors—like confounds 2. What broad categories define control strategies?- Participant assignment - Experimental design details- Logic of experimental design3. Why is random assignment critical to internal validity? In theory, what is random assignment designed to accomplish?- Any change in our DV is truly the reflection of our IV and that variable alone- Random assignment is designed to make groups similar at the outset of the study4. If you were designing an experiment on a variable or variables that have already been widely studied, how might a thorough literature review of the existing research help you determine how to best increase the control in your own study?- If we know of variables that may influence our results (outside of IV), we can try to control for them deliberately5. What is matching? Why and when is it used?- Matchingo Pre-test participants on their ability to complete task, based on that ability, pair them up and assign a member of each pair to a different condition within the experiment. - Why?o By doing this it equates ability of task at the outset of the study- When?o If we know of variables that may influence our result (outside the IV), we can try to control for them deliberately6. What two functions is any experiment designed to address?- Provide evaluation of effects of IV on DV- Help rule out confounds7. Be familiar with a pretest-posttest control group design. Be able to recognize such a design if given an example of one.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Randomly assign participants to groups (control/experimental)o Give pre-test to each group BEFORE treatment Compare for similarityo Give posttest to each group AFTER treatment Compare to evaluate treatment effect- EXAMPLE: HA: new reading program will increase reading comprehension in 2nd grade childreno Randomly assign:52 children to control & experimental/treatment groups:Experimental grp(26 children)Reading Pretest Treatment (IV) (reading program)Reading posttestControl grp Reading Pretest No Treatment (noIV) (no reading program)Reading posttest8. What are the advantages and disadvantages associated with a pretest-posttest control group design?- Benefitso Allows to determine if 2 groups are equal on DV before treatment - Disadvantageso Possible that pretest may influence outcome of the experiment 9. What additional aspect of control is addressed with the Solomon Four Group design?- Controls o History o Maturation10. Be able to diagram the Solomon Four Group Design. Be able to recognize such a design if given an example of one.- Arrangement checks for possibility that pretest influences the results of the experimentGroup 1 Pretest Treatment (IV) PosttestGroup 2 Pretest No Treatment (no IV) PosttestGroup 3 ----------- Treatment (IV) PosttestGroup 4 ----------- No Treatment (no IV) Posttest11. In the Solomon, what three comparisons collectively allow you to evaluate the internal validity of your study? What does each of these comparisons tell you specifically? What combination of results would best allow you to conclude that (i.e., give you the greatest confidence) any difference in the DV is truly the result of the IV and not some other variable?- To determine if IV affected DV (treatment effect)o Compare groups 1 & 2 posttest score Treatment=different, no treatment=similar- To determine if pretest confounded any effect of the IVo Compare group 1 & 3 posttest If pretest had no effect=similar, treatment effect=different- To determine if pretest alone affected DVo Compare groups 2 & 4 posttest Treatment=different, no treatment=similar- Combination of results for greatest confidenceo Group 1 &2 have different posttest scoreso Group 1 & 3 have similar posttest scoreso Group 2 & 4 have similar posttest scores12. If given results from a Solomon Four Group design, would you be able to identify the important comparisons and interpret their meaning in terms of confounds and internal validity?- Pretest increases internal validity by insuring that the participants in 2 conditions are equated on the DV measures at the outset of study- If pretest scores were different there are 2 solutionso Reassign participants to equate the DV measureso Evaluate the treatment effect as a “difference score”(post-pre score) to account for the different starting points at pretest13. What are the broad differences between a between-subject, within-subject and mixed design?- Between-subjectso Different participants are assigned to different conditionso Different individuals receive different levels of the IV- Within-subjectso Same participants serve in all conditions o Same individuals receive all levels of IVo Participants serve as their own controls- Mixed o Examines at least 2 IVs at same time  At least 1 IV run between-subjects At least 1 IV run within-subjects14. What three types of between-subject design arrangements were covered in class? Could you identify each if given an example? If given a hypothesis, could you design an experiment using these designs (as appropriate to the research question being tested)?- Completely randomizedo Examines 1 IV w/ 2 levels (IV; no IV) Participants randomly assigned to either control or treatment  ½ assigned to control, ½ assigned to treatment Music example (experimental-music, control-no music)- Multi-level completely randomizedo Examines IV w/ 3 or more levels Random assignment of participants to different groups E.g., if 3 levels, 1/3 participants in each condition Music example (rock music, classical music, no music-control)- Factorial designso Examines effects of 2 or more IVs on the same DV in same studyo Each IV must have at least 2 levels (IV, no IV), could have more15. What is the difference between a “factor” and a “level” in factorial design? When do you use a factorial design arrangement?- Factor=IV- Level=within the IV (IV or no IV, could have more)- Used when you have 2 or more IVs on the same DV in the same study16. Could you identify factors and levels of the IVs if given examples of experiments (as youdid in Assignment #5)?- Example: Does the effect of music on