Author(s) Mike Kardas (University of Chicago) - mkardas@wisc.edu Alex Shaw (University of Chicago) - alex.w.shaw@gmail.com Eugene Caruso (University of Chicago) - eugene.caruso@gmail.com
Pre-registered on 2017/11/14 22:22 (PT)
1) Have any data been collected for this study already? It's complicated. We have already collected some data but explain in Question 8 why readers may consider this a valid pre-registration nevertheless.
2) What's the main question being asked or hypothesis being tested in this study? See AsPredicted #5429.
3) Describe the key dependent variable(s) specifying how they will be measured. See AsPredicted #5429.
4) How many and which conditions will participants be assigned to? See AsPredicted #5429.
5) Specify exactly which analyses you will conduct to examine the main question/hypothesis. See AsPredicted #5429.
6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations. See AsPredicted #5429.
7) How many observations will be collected or what will determine sample size? No need to justify decision, but be precise about exactly how the number will be determined. We are amending pre-registration #5429. Specifically, we began collecting data from an outdoor location on 9/27/17 and expected to collect the sample of N = 256 participants after exclusions before temperatures became prohibitively cold in December. However, data collection has been slower than expected because additional studies that were not active when we launched on 9/27 have since competed with our own study for data collection time at this outdoor study location.
With N = 91 participants after exclusions, we currently observe large and significant differences in choices between the baseline (39% generosity) and abdication (71% generosity) conditions, Z = 3.03, p = .002, 95% CIdifference = [11%, 53%]. Because we would need to wait several months until spring to finish collecting data from the same outdoor setting, we plan to collect as many data points as we can through the end of November and then conduct final analyses. The final day of data collection will be November 30th.
To test the robustness of the current effect,we also examined whether the current effect would remain significant if additional data did not support our hypothesis. If we were to continue with our original plan of collecting N = 128 participants in both the “baseline” and “abdication” conditions, and if the remaining participants in both conditions responded at random (i.e., 50% of remaining participants in both conditions were generous and 50% were not), we would still observe significant differences in rates of generosity among the entire sample between the baseline (47%) and abdication (59%) conditions, Z = 2.00, p = .046. Given that we have also observed significant differences between the baseline and abdication conditions in pre-registered online studies, the null effect size seems unlikely, and hence the effect would seem highly likely to remain significant if we were to collect the full sample. Therefore, considering prohibitively cold temperatures, we now intend for the final day of data collection to be November 30th.
8) Anything else you would like to pre-register? (e.g., secondary analyses, variables collected for exploratory purposes, unusual analyses planned?) We are amending pre-registration #5429 (see #7 for notes about sample size).
