#64626 | AsPredicted

'Update to aspredicted #64246'
(AsPredicted #64626)

Created:       04/28/2021 03:34 PM (PT)

This is an anonymized version of the pre-registration.  It was created by the author(s) to use during peer-review.
A non-anonymized version (containing author names) should be made available by the authors when the work it supports is made public.

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?
This is an update to a previous pre-registration (aspredicted # 64246). See the main question on aspredicted #64246.

3) Describe the key dependent variable(s) specifying how they will be measured.
Same as aspredicted #64246

4) How many and which conditions will participants be assigned to?
Same as aspredicted #64246

5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
Same as aspredicted #64246

6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations.
Since recruitment on Mturk is very slow, maybe because we have almost exhausted the non-vaccinated Mtruk population, we plan to expand recruitment to Prolific Academic. We will continue running the study on Mturk following the same inclusion and exclusion criteria listed in aspredicted #64246

For Prolific Academic, we will first use the Prolific prescreening options to recruit participants who are not-vaccinated. We will further use a question in the survey to screen out participants who are not vaccinated and do not have an upcoming appointment. Participants will be included in our data analysis if they satisfy the following criteria:
-Pass an attention check question assessing whether participants are reading instructions closely
-Have not already received the COVID-19 vaccine or had an appointment
-Answer our primary dependent variables (Section 3).
-Report having no problems with watching the video
-Report either having not taken a similar study on Mturk or that they cannot remember (i.e., excluding people who report having taken a similar study)

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.

On top of recruiting on Amazon Mechanical Turk from 9am PST to 7pm PST for 7 consecutive days, as detailed in aspredicted #64246, we will attempt to recruit another 400 participants on Prolific Academic in order to reach a total sample size of 1000 non-vaccinated people who satisfy our criteria (described in Section 6) across the two recruitment platforms.

8) Anything else you would like to pre-register?
(e.g., secondary analyses, variables collected for exploratory purposes, unusual analyses planned?)

Same as aspredicted #64246.
We have added this pre-registration because data collection on Mturk has been extremely slow and we project that by the end of the 7th day of data collection we will only have about 600 observations. For this reason, we plan to recruit a