'COVID vaccine intentions - Study 3' (AsPredicted #69185)
Author(s) This pre-registration is currently anonymous to enable blind peer-review. It has 4 authors.
Pre-registered on 2021/06/24 - 06:31 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. Multiple exposure to a fake news story about the COVID-19 vaccine will increase its perceived accuracy relative to a single exposure.
2a. Exposure to a fake news story that is negative about the COVID-19 vaccine will decrease intentions to be vaccinated relative to exposure to neutral stories.
2b. Exposure to a fake news story that is positive about the COVID-19 vaccine will increase intentions to be vaccinated relative to exposure to neutral stories.
3a. Multiple exposure to a fake news story that is negative about the COVID-19 vaccine with a 3(±1) days delay will decrease intentions to be vaccinated relative to multiple exposure to neutral stories or to a single exposure to a negative story.
3b. Multiple exposure to a fake news story that is positive about the COVID-19 vaccine with a 3(±1) days delay will increase intentions to be vaccinated relative to multiple exposure to neutral stories or to a single exposure to a negative story.
3) Describe the key dependent variable(s) specifying how they will be measured. The primary DV is the response 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 six conditions with a 3x2 design:
A. News condition:
1. 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 randomly-selected true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
2. 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 randomly-selected true news stories which relate to COVID-19 but do not mention vaccines or have any implications for vaccination decision-making.
3. 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.
B. Exposures
1. Single exposure: Participants will be exposed once to each story and will be asked after each "How accurate do you believe the above headline is?" with a 5-point scale ranging from 1 (Very inaccurate) to 5 (Very accurate). They will then be presented with the behavioural intention items.
2. Multiple exposure: Participants will be exposed to each story and asked after each "do you remember the events described in this story?", with a 4-point scale: (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. Two to four days later, they will be invited to a follow up study, where they will be exposed to the same novel stories about the COVID-19 vaccine, but different true neutral stories. After each story, they will be asked "How accurate do you believe the above headline is?" with a 5-point scale ranging from 1 (Very inaccurate) to 5 (Very accurate). They will then be presented with the behavioural intention items.
5) Specify exactly which analyses you will conduct to examine the main question/hypothesis. Two two-samples t-tests will be conducted, comparing the accuracy scores of the fake news items between the single exposure and multiple exposure conditions. The first analysis will compare the two positive fake news groups, and the second the two negative fake news groups.
A two-way analysis of variance with post hoc Tukey tests will also be conducted in which the IVs are the news condition and the number of exposures, and the DV is responses on the COVID vaccination intention question.
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 indicate that have already received at least one dose of a COVID-19 vaccine or fail an attention check question. The attention check will be presented with the behavioural intention items.
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 1548, which provides 95% power to detect effects of size f = 0.1 in a two-way ANOVA with a 3x2 design.
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 and exposures 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) and of the length of the delay between first and second exposure.
