Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and Booking Intention: Online Experiment 2
Phase: NA
Conditions: Vaccination
Sponsor: University of Essex

Document related to the study: “Optimizing Weblinks Used in Digital 
Vaccination Invitations to Raise Trust and Booking Intention: Online 
Experiment 2” 
 
The document was registered on AsPredicted on the 01/11/2022 
 
 
The document includes hypotheses, design, dependent variables and analytical plan for the 
study “Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and 
Booking Intention: Online Experiment 2” 

Version of AsPredicted Questions: 2.00
PDF generated: 2026/02/09 01:42 (PT)
Available at https://aspredicted.org/3zm5-7hpk.pdf
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Trustworthy links and vaccination_S2 (#84816)
Author(s)
This pre-registration is currently anonymous to enable blind peer-review.
It has one author.
Pre-registered on:
2022/01/11 05:12 (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?
Participants will read one of three emails of invitation to get a booster vaccine.
One email will include the accurx web link that was based on the NHS link (e.g., in text invites), the second will include a shortened version of the
link (bit.ly) and the third will show the link as a hyperlink.
The UK and US samples will be shown slightly diﬀerent emails (sent by the NHS in the UK and from Pharma-US in the US).
1. The email that includes the accurx web link will be perceived as less trustworthy, than the other emails.
2. Participants will be less likely to agree to book a vaccine appointment based on the accurx web link email than in the other conditions.
3. Participants will ﬁnd the accurx link less ﬂuent than the other two web links.
4. Participants will be less likely to identify the organisation that hosts the link based on the accurx web link than based on the other two.
5. Trustworthiness, likelihood to book and likelihood to correctly identify the host organisation and ﬂuency will be positively correlated with each
other
6. The eﬀect of the link will be mediated by the correct/incorrect identiﬁcation of the host organisation and the ﬂuency of the link
3) Describe the key dependent variable(s) specifying how they will be measured.
Participants will rate each text message in terms of how trustworthy it seems on a 5 point Likert scale (1: Very suspicious to 5: very trustworthy),
how ﬂuent is the link on a 5 point Likert scale (1: very diﬃcult – 5: very easy) and how likely they would be to book an appointment on a 5 point
Likert scale (1: very unlikely to 5: very likely). To identify the host organisation of the website, participants will select one answer from a list of four
possible answers (the NHS, pharma-us, accurx or unclear/I don't know).
4) How many and which conditions will participants be assigned to?
Participants will be randomly allocated to one of the three email conditions. Participants will see the UK or US version as a function of their country of
residence.
5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
We will test hypotheses 1-3 with a within-subject analysis of variance with the web link manipulation (3 conditions) and the country (US vs. UK) as
between subject factors and the diﬀerent variable about the email perception as dependent variables.
We will test hypothesis 4 using a chi square.
We will test hypothesis 5 using a correlational analysis.
We will test hypothesis 6 using a mediation analyses.
If we ﬁnd some interaction eﬀects with country of residence, we might test the eﬀects in the two countries separately.
We will also test the robustness of the eﬀect by including participants' sociodemographic characteristics (e.g., gender, age, education).
6) Describe exactly how outliers will be deﬁned and handled, and your precise rule(s) for excluding observations.
We will ﬁlter participants out if we judge they completed the study too fast or failed the attention check.
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 will invite 1200 participants to complete an online study (600 from the US and 600 from the UK).
8) Anything else you would like to pre-register? (e.g., secondary analyses, variables collected for exploratory purposes, unusual
analyses planned?)
This study is part of the online questionnaire which includes other questions (e.g., about the perceived trust of vaccination invitation sent via text
messages).