1. First the multi choice, then the complex one.

2. A professor was curious about the impact of student diet, especially sugar and caffeine, on test performance. She invited students from her classes to participate in a study before their mid-term exams. Forty students accepted the invitation to participate. The professor randomly assigned them to her experimental groups. The students in one group were told not to change their food and drink consumption during the week before their exams but to record everything they ate and drank in a diary. The students in the second group were also asked to record their nutritional intake in the same kind of diary, but were also given unlimited free coffee at the campus coffee shop. The students in the third group received both free coffee and free donuts at the coffee shop, and again were asked to record everything they ate and drank in a diary. The professor planned to use the average of their mid-term grades in her classes as the dependent variable.

3.  a) the independent variable  Diet (3 levels: normal vs caffeine vs sugar and caffeine) (100%)  b) the dependent variable  Test performance (100%)  c) the study design using design notation RX 1 O RX 2 O R X 3 O(80%)

4.  From the rubric questions:  What is the relationship being studied? ▪ A professor was curious about the impact of student diet, especially sugar and caffeine, on test performance ▪ This will provide the starting and finishing point for all critiques (the next would too, usually, but as you’ll see...)  What are the study findings, if any? ▪ None – no data collected yet.

5.  What is the sampling strategy?  Well, she is a professor, and “She invited students from her classes to participate in a study before their mid-term exams. Forty students accepted the invitation to participate.”  SO: 1.It is non-probabilistic 2.It is a sample of convenience 3.It is a volunteer study (not all will have volunteered)

6.  To what population/time/setting is the study being generalized/targeted (either implied or actual)? (Look for author wording confirming the attempted generalization)  A professor was curious about the impact of student diet, especially sugar and caffeine, on test performance ▪ The only qualifiers are that she is interested in students’ diets, and she is interested in its effects on test performance only. ▪ So there is something about population (students) and something about setting/timing (effects on test performance – so being applied to when they are taking a test) ▪ The test performance will be taken care of by construct validity (it’s one of the constructs in the study, so doesn’t need to be considered here)...so we’ll restrict ourselves to the population issue here. ▪ Also all recorded their food consumption in a diary (part of study settings)

7.  What does the sampling strategy and the actual time and settings of the study imply about the merits of any generalization found in (b) above? (Is there a good match, or do you see some mismatches?)  Ok, now we get to the crux of it. Does allowing volunteers from her classes in some way provide a biased sample for the study, such that these students do not adequately represent other students? Or in other settings? ▪ Clearly there are potential problems here. It is very likely that this sample has systematic differences from the general population due to ▪ All participants are from one college, one department, one instructor’s classes ▪ All participants are volunteers ▪ All recorded their food intake (general population does not, explicitly anyway)

8.  To what extent do you think there is a problem of generalization? In other words, do you think the relationship under investigation (see 1.B.), or the results of the study (see 1.C.) would have potential to change given any of the issues raised in 2.C?  To answer this question, we have to consider: ▪ What moderator variables might have been unwittingly introduced by the sampling strategy ▪ Whether these moderators could interact with the study variables  So what moderators do we have? ▪ SES? Education level? ▪ Interest in research? Responsibility? ▪ Overall awareness/recall of diet? Based on one college etc. Based on volunteerism. Based on diaries.

9.  But ultimately the goal is to provide a rationale as to whether your moderators would in fact interact with the study findings (have the potential to change them)  SES? Education level? ▪ Could this change the results of a study looking at diet and performance? ▪ (e.g. if these students were more or less than typically capable, would they be more or less susceptible to effects of sugar and/or caffeine on test performance? Well – maybe there’s something to do with test anxiety here? Or competence? Or both?)  Interest in research? Responsibility? ▪ Could this change the results of a study looking at diet and performance? ▪ (e.g. if people are more interested in research, are they more likely to be the kind of disciplined student whose preparation for the test is diligent enough to allay crises of confidence? Or are they likely to be precisely the people who have such crises of confidence, and therefore be more likely to participate...and be more sensitive to the effects of caffeine/sugar dosing) Should be considered but a definitive answer is not needed for an “A”

10.  What are the constructs in the study intended to measure?  State the idea(s) behind the dependent measures  State the idea(s) behind the independent measures  Test Performance:  Likely, a capacity to produce competent academic work in a stressful situation.  Type of work/test? Duration?  Diet (especially sugar and caffeine):  Probably getting at energy highs and lows, and memory and cognition type effects, and the supposed effects of S & C  Sugar and caffeine...what are the supposed effects? When do they exert their influence? Long term? Short term? Dose?  Likely you’d have further questions about these 2 from a “full paper”

11.  How is each construct in the study operationalized?  State how dependent measures are operationalized  State how independent measures are operationalized  Dependent measure:  Average of mid-term grades  Independent measure:  Influenced via free coffee, doughnuts (depending on group assignment) at campus coffee shop.  Self-reported via diary

12.  What are the strengths and/or weaknesses of the observed operationalizations?  Consider the types of validity: face, content, etc.  Consider the laundry list of threats.  Do so for both constructs!  Mid-term grades representing test performance  Has face validity...looks right. Details? What kind of test was the mid- term? This was only one kind of test...how hard was it? Multi-choice? Essay? Timed? Untimed? Level of class (es)? Need more details!  Diet and free coffee/doughnuts  Did they actually partake? Did all of them? On a consistent basis? What we really expect to see are elevated levels of caffeine and or sugar in the diet (for the treatment groups). Is this going to achieve it?  No control of dose, so potentially very weak operationalization.  Self-report has recall/honesty issues

13.  Is the construct validity issue as described in previous slide likely to alter the results of the study?  Midterm grades:  Could. What does the effect depend on? Exam stress and it’s response? If so, an easy test might mean a null response, a difficult test an exaggerated one (unable to focus…more stress..etc).  Diet:  Could: If the resultant dosing was too low on average across either group, then null results might come out. Might also get great variability within groups.  If accuracy of diary method is serious, might also get discrepancies (if factoring into analysis by controlling for reported level of dose) Should be considered, but a definitive answer is not needed for an “A”

14.  What is the study’s design? RX 1 O RX 2 O R X 3 O

15.  Does the study’s design establish temporal precedence?  Yes.

16.  Does the study’s design establish covariation of cause and effect?  Yes, partly and potentially. ▪ There is an available comparison of normal versus raised coffee intake. (However, of course, they may not have drunk more) ▪ The potential for increased sugar intake is only available when paired with potential increased caffeine intake – so covariation is compromised for that variable.

17.  To what extent does the study’s design control for alternate interpretations of the causal relationship? Does it control for:  Single group threats? ▪ yes  Multiple group threats? ▪ Yes (random assignment – and 40 seems an adequate number, though you could argue this.).  Social interaction threats? ▪ Nope.

18.  Using your response to A-D, to what extent is the assertion that the relationship under investigation is causal a reasonable one?  While groups were probably equal at the start of the experiment, the fact that they all attended the same classes suggests they may have become aware of the alternate conditions of the experiment.  The nature of the conditions was such that numerous social issues could have arisen.

19.  In the event of observed weak internal validity, can you suggest an alternative causal interpretation?  Can the social issues change the results of the experiment? ▪ Possibly. ▪ Frustration and feeling cheated could conceivably result in people in the control group over-compensating by trying harder, or feeling aggrieved and getting extra stressed and doing poorly. ▪ Note the different pattern of results these possibilities would result in. Should be considered, but a definitive answer is not needed for an “A”