#68730 | AsPredicted

'COVID vaccine intentions - Study 2'
(AsPredicted #68730)


Author(s)
This pre-registration is currently anonymous to enable blind peer-review.
It has 4 authors.
Pre-registered on
06/17/2021 11:05 AM (PT)

1) Have any data been collected for this study already?
No, no data have been collected for this study yet.

2) What's the main question being asked or hypothesis being tested in this study?
1. Exposure to a true or fake negative story about the COVID-19 vaccine will decrease intentions to be vaccinated, relative to exposure to neutral stories.
2. Exposure to a true or fake positive story about the COVID-19 vaccine will increase intentions to be vaccinated, relative to exposure to neutral stories.

3) Describe the key dependent variable(s) specifying how they will be measured.
The primary DV is responses to the statement, "I intend to get a COVID-19 vaccine" on a 7-point Likert scale ranging from 1 (Strongly disagree) to 7 (Strongly agree).
A series of other behavioural intention statements will also be measured using the same scale.

4) How many and which conditions will participants be assigned to?
Participants will be randomly assigned to one of five conditions:
1. Negative fake news: Participants will view one novel, fabricated news headline containing untrue information that is negative about the COVID-19 vaccine, selected from a pool of 5 such stories. Participants in this condition will also view two true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
2. Negative real news: Participants will view one true news headline containing information that is negative about the COVID-19 vaccine, selected from a pool of 5 such stories. Participants in this condition will also view two true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
3. Positive fake news: Participants will view one novel, fabricated news headline containing untrue information that is positive about the COVID-19 vaccine, selected from a pool of 5 such stories. Participants in this condition will also view two true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
4. Positive real news: Participants will view one true news headline containing information that is positive about the COVID-19 vaccine, selected from a pool of 5 such stories. Participants in this condition will also view two true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
5. Control condition: Participants will view three randomly-selected true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.

After viewing each story, participants will be asked, "do you remember the events described in this story?", and can select from the following options:
1. I have a clear memory of seeing/hearing about this
2. I have a vague memory of this event occurring
3. I remember this differently
4. I don't remember this

5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
Two one-way analyses of variance with post hoc Tukey tests will be conducted in which the IV is the news condition and the DV is responses on the COVID vaccination intention question. The first analysis will compare the negative fake news, negative real news, and control conditions. The second analysis will compare the positive fake news, positive real news, and control conditions.

6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations.
Participants will be excluded from analysis if they fail an attention check question or indicate that have already received at least one dose of a COVID-19 vaccine.

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.

The final sample size (following exclusions) will be 1615, with 323 participants per condition. This will provide 969 participants for each of the one-way ANOVA, with a 80% power to detect effects of size f = 0.1.

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

We will also examine the effect of news condition on responses to the other health behaviour statements to determine whether any effect is specific to COVID-19 vaccination intentions.
Exploratory analysis will also examine the moderating effect of existing vaccine opinions (based on participant responses to prescreening questionnaires on Prolific).