I conduct an online study to determine whether rewards reduce procrastination. All participants are asked to complete a task sometime before a deadline (10 days from now). The computer randomly assigns partici one of three groups, and emails them their instructions; one group receives a reward as soon as they do the task (contingent reward); a second group receives rewards as soon as they finish the task as long as it is b deadline (non-contingent reward) and the third group does not receive rewards at all (no reward). Three participants in the no reward condition do not complete the task, and so are dropped from analyses. The depe variable is the amount of time (in days) it takes participants to complete the task. The JAMOVI output is attached. What are possible threats to internal validity in this study (select all that apply)? ANOVA ANOVA-Time Reward Residuals Sum of Squares df Mean Square F 68.852 2 125.814 24 Assumption Checks Homogeneity of Variances Test (Levene's) Р n'p 34426 6.567 0.005 0.354 5.242

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I conduct an online study to determine whether rewards reduce procrastination. All participants are asked to complete a task sometime before a deadline (10 days from now). The computer randomly assigns participants to
one of three groups, and emails them their instructions; one group receives a reward as soon as they do the task (contingent reward); a second group receives rewards as soon as they finish the task as long as it is before the
deadline (non-contingent reward) and the third group does not receive rewards at all (no reward). Three participants in the no reward condition do not complete the task, and so are dropped from analyses. The dependent
variable is the amount of time (in days) it takes participants to complete the task. The JAMOVI output is attached.
What are possible threats to internal validity in this study (select all that apply)?
ANOVA
ANOVA - Time
Reward
Residuals
0.056
Assumption Checks
Homogeneity of Variances Test (Levene's)
F
df1
Statistic
0.964
Sum of Squares df
68.852 2
125.814 24
Normality Test (Shapiro-Wilk)
2
Post Hoc Tests
Reward
Contingent
df2
24
P
Post Hoc Comparisons - Reward
Comparison
0.444
Mean Square F
Р
0.945
Reward
P
n'p
34.426 6.567 0.005 0.354
5.242
Non-contingent
No reward
No reward
Mean Difference SE
-3.700
-2.129
1.571
Non-contingent -
Note. Comparisons are based on estimated marginal means
df
t Ptukey
0.004
1.024 24.000 -3.613
1.128 24.000 -1.886 0.164
1.128 24.000 1.393 0.360
Transcribed Image Text:I conduct an online study to determine whether rewards reduce procrastination. All participants are asked to complete a task sometime before a deadline (10 days from now). The computer randomly assigns participants to one of three groups, and emails them their instructions; one group receives a reward as soon as they do the task (contingent reward); a second group receives rewards as soon as they finish the task as long as it is before the deadline (non-contingent reward) and the third group does not receive rewards at all (no reward). Three participants in the no reward condition do not complete the task, and so are dropped from analyses. The dependent variable is the amount of time (in days) it takes participants to complete the task. The JAMOVI output is attached. What are possible threats to internal validity in this study (select all that apply)? ANOVA ANOVA - Time Reward Residuals 0.056 Assumption Checks Homogeneity of Variances Test (Levene's) F df1 Statistic 0.964 Sum of Squares df 68.852 2 125.814 24 Normality Test (Shapiro-Wilk) 2 Post Hoc Tests Reward Contingent df2 24 P Post Hoc Comparisons - Reward Comparison 0.444 Mean Square F Р 0.945 Reward P n'p 34.426 6.567 0.005 0.354 5.242 Non-contingent No reward No reward Mean Difference SE -3.700 -2.129 1.571 Non-contingent - Note. Comparisons are based on estimated marginal means df t Ptukey 0.004 1.024 24.000 -3.613 1.128 24.000 -1.886 0.164 1.128 24.000 1.393 0.360
Estimated Marginal Means
Reward
Time
10.0
7.5
5.0
2.5
Contingent Non-contingent
Reward
Estimated Marginal Means - Reward
:
Reward
Mean SE
Contingent
4.300 0.724
Non-contingent 8.000 0.724
No reward
6.429 0.865
No reward
95% Confidence Interval
Lower
Upper
2.806
6.506
4.643
5.794
9.494
8.215
a. Carry-over between experimental conditions
Ob. Experimenter bias
c. Mortality/Attrition in the no Reward group
Od. Students are not representative of the general population
Transcribed Image Text:Estimated Marginal Means Reward Time 10.0 7.5 5.0 2.5 Contingent Non-contingent Reward Estimated Marginal Means - Reward : Reward Mean SE Contingent 4.300 0.724 Non-contingent 8.000 0.724 No reward 6.429 0.865 No reward 95% Confidence Interval Lower Upper 2.806 6.506 4.643 5.794 9.494 8.215 a. Carry-over between experimental conditions Ob. Experimenter bias c. Mortality/Attrition in the no Reward group Od. Students are not representative of the general population
Expert Solution
Step 1

The possible threats for the internal validity:

  • Maturation: Increase of time may influences the dependent variable.
  • Participants selection: Participants selected by using random assignment.
  • Attrition: Participants may drop out over the study.
  • Testing: Results of one experimental group affects the results of another experimental group.

 

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