Pre-Analysis Plan: A field experiment providing information on polls in South Africa 2019 study

Last registered on January 22, 2026
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Pre-Trial

Trial Information

General Information

Title
Pre-Analysis Plan: A field experiment providing information on polls in South Africa 2019 study
RCT ID
AEARCTR-0017627
Initial registration date
January 14, 2026

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
January 22, 2026, 6:28 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

Country
South Africa
Region

Primary Investigator

Name
Brynde Kreft
Affiliation
Oxford University
Contact Primary Investigator

Other Primary Investigator(s)

PI Name
Kate Orkin
PI Affiliation

Additional Trial Information

Status
Completed
Start date
2019-04-05
End date
2019-04-19
Keywords
Behavior, Electoral
Additional Keywords
JEL code(s)
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
Abstract
This is the analysis plan for an experiment showing election polls to potential voters in multiple locations in South Africa. The study complements a previous experiment (Orkin, 2016).

This study is a survey experiment conducted as part of a nationally-representative opinion
poll of 1,300 adults by the research company Citizen Surveys. The survey is conducted the
month before the May 2019 elections. I conduct two separate experiments in two groups of
provinces: the competitive and uncompetitive. In the former group, where the election for
the provincial assembly is close, respondents are randomly allocated to 3 equal groups: a
control group and two treatment arms. The two treatment groups are each read an opinion
poll in which the election is predicted to be close; the two polls vary only in which party
is leading the race. In the latter group of provinces, where the incumbent African National
Congress (ANC) party is almost certain to win an outright majority, the respondents are also
split into a control and two treatment groups. Treated individuals hear a hypothetical poll,
with the two treatments varying the margin of ANC’s lead over the remaining parties.
At the time of lodging this analysis plan, the treatment assignment has been received from
the polling company but has been stored by a research assistant, Marta Grabowska, in a
separate, encrypted location the PIs cannot access. Marta has constructed the variables of interest
in order to check for data quality issues, but conducted no analysis of treatment effects.
External Link(s)

Registration Citation

Citation
Kreft, Brynde and Kate Orkin. 2026. "Pre-Analysis Plan: A field experiment providing information on polls in South Africa 2019 study." AEA RCT Registry. January 22. https://doi.org/10.1257/rct.17627-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
The study comprises two experiments, each with three treatment arms.

Experiment 1:
There are three treatment groups in this experiment, the control group and two treatment
arms. The control group receive no treatment: they just proceed to the follow-up module.
Individuals assigned to treatment received one of two information messages. The messages
each give two pieces of information: an opinion poll for the upcoming provincial race, and
that there are many undecided voters who may swing the outcome of the provincial election.9
The opinion polls differ in the two treatments. Specifically:
Message 1: The poll puts the DA at 40% of vote share, the ANC at 38% and the EFF at
10%.
Message 2: The poll puts the ANC at 40% of vote share, the DA at 38% and the EFF at
10%.

Experiment 2:
There are three treatment groups in this experiment, the control group and two treatment
arms. Messages are similar in structure to experiment 1, except the opinion polls used are
different:
Message 1: The poll puts the ANC at 70% of vote share, with the DA and EFF at 15%
each.
Message 2: The poll puts the ANC at 60% of vote share, with the DA and EFF at 15%
each.

Intervention (Hidden)
Intervention Start Date
2019-04-05
Intervention End Date
2019-04-19

Primary Outcomes

Primary Outcomes (end points)
Voting motivation, predicted turnout behaviour, voting intention.
Primary Outcomes (explanation)
Voting motivation - elicited from a likert-type scale. We will analyse both binary and scale responses.
Predicted turnout behaviour - a predicted turnout indicator equal to 1 if the respondent meets the following conditions: is registered to vote, is able to overcome voting day challenges and is motivated to vote. This measure will identify whether any changes in the motivation measure depended on differential ability to cast one’s vote.
Voting intention.- A categorical variable, each category representing the party which the respondent intends to vote for.

Secondary Outcomes

Secondary Outcomes (end points)
Party quality perception index, expected election winner, expected vote share of each party, expectation that the election will be close, level of certainty about expected winner of the election.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The study comprises two experiments.
1. Experiment 1: This experiment is conducted in the provinces where the public polls predicted the election would be close. There are two polls, both of which say the provincial election is close. They vary only which of the two parties, ANC or the DA, is just ahead. The third party, the Economic Freedom Fighters (EFF), is far behind.

2. Experiment 2: This experiment is conducted in the provinces where the ANC is likely to win a large outright majority. The two treatment messages both give polls which state the ANC is likely to win the provincial race. The polls vary how much the ANC is predicted to be leading by. The DA and EFF are tied in second place.
Experimental Design Details
Randomization Method
Treatment is assigned randomly at the individual level by the survey software.
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
1300 individuals
Sample size: planned number of observations
1300 individuals
Sample size (or number of clusters) by treatment arms
Experiment 1:
279 control, 284 DA lead, 281 ANC lead

Experiment 2:
148 control, 155 ANC 70%, 153 ANC 60%
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Central University Research Ethics Committee Oxford
IRB Approval Date
2019-03-22
IRB Approval Number
Details not available
Analysis Plan

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Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials