Consumer preferences for organic and local apples

Last registered on January 30, 2023
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Pre-Trial

Trial Information

General Information

Title
Consumer preferences for organic and local apples
RCT ID
AEARCTR-0010823
Initial registration date
January 24, 2023

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 30, 2023, 1:19 AM EST

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

Locations

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Primary Investigator

Name
Andreas Drichoutis
Affiliation
Agricultural University of Athens
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Other Primary Investigator(s)

PI Name
Marija Cerjak
PI Affiliation
University of Zagreb Faculty of Agriculture
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PI Name
Josip Juračak
PI Affiliation
University of Zagreb Faculty of Agriculture
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PI Name
Damir Kovačić
PI Affiliation
University of Zagreb Faculty of Agriculture
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Additional Trial Information

Status
In development
Start date
2023-01-26
End date
2023-04-15
Keywords
Behavior
Additional Keywords
second price auction, organic apples, local apples, willingness to pay, WTP
JEL code(s)
C91, D12, M31
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This study elicits consumers' preferences for organic and local attributes of apples and also examines the effect of information provision and taste. Subjects are recruited from the population of the wider area of Zagreb in Croatia and participate in a second price auction where they bid to buy 1 kilo of apples. Subjects are randomly assigned to one of the following treatments, where we vary on a between-subjects basis the apples available for auction. Subjects bid simultaneously for two of the apples:

Treatment 1: Organic - Local apple vs. Conventional - Local apple
Treatment 2: Organic - Local apple vs. Organic - non-Local apple
Treatment 3: Conventional - non-Local apple vs. Conventional - Local apple
Treatment 4: Conventional - non-Local apple vs. Organic - non-Local apple

Subjects go through three rounds of auctions. In the first round they have no information about the attributes of the apples and they are asked to bid based on appearance only. In Round 2, they receive information about the apples and in Round 3 they get to taste the apples before they bid.
External Link(s)

Registration Citation

Citation
Cerjak, Marija et al. 2023. "Consumer preferences for organic and local apples." AEA RCT Registry. January 30. https://doi.org/10.1257/rct.10823-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Subjects receive a 20 Euro coupon for participation and then participate in a zero counting task for 10 rounds, where they can earn up to 50 cents per round, so that they make up to 5 Euros by round 10. They are told from the beginning that for only 1 subject in each group their decisions will be realized and only for that subject earnings from the zero counting task and winnings from the auction are realized.

Subjects are randomly assigned to one of the following treatments, where we vary on a between-subjects basis the apples available for auction. Subjects bid simultaneously for two of the apples:

Treatment 1: Organic - Local apple vs. Conventional - Local apple
Treatment 2: Organic - Local apple vs. Organic - non-Local apple
Treatment 3: Conventional - non-Local apple vs. Conventional - Local apple
Treatment 4: Conventional - non-Local apple vs. Organic - non-Local apple

Subjects go through three rounds of auctions. In the first round they have no information about the attributes of the apples and they are asked to bid based on appearance only. In Round 2, they receive information about the apples and in Round 3 they get to taste the apples before they bid. The overall design combines elements of within- and between-subjects design.

Intervention Start Date
2023-01-26
Intervention End Date
2023-04-15

Primary Outcomes

Primary Outcomes (end points)
Bid
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Subjects receive a 20 Euro coupon for participation and then participate in a zero counting task for 10 rounds, where they can earn up to 50 cents per round, so that they make up to 5 Euros by round 10. They are told from the beginning that for only 1 subject in each group their decisions will be realized and only for that subject earnings from the zero counting task and winnings from the auction are realized.

Subjects are randomly assigned to one of the following treatments, where we vary on a between-subjects basis the apples available for auction. Subjects bid simultaneously for two of the apples:

Treatment 1: Organic - Local apple vs. Conventional - Local apple
Treatment 2: Organic - Local apple vs. Organic - non-Local apple
Treatment 3: Conventional - non-Local apple vs. Conventional - Local apple
Treatment 4: Conventional - non-Local apple vs. Organic - non-Local apple

Subjects go through three rounds of auctions. In the first round they have no information about the attributes of the apples and they are asked to bid based on appearance only. In Round 2, they receive information about the apples and in Round 3 they get to taste the apples before they bid. The overall design combines elements of within- and between-subjects design.
Experimental Design Details
Not available
Randomization Method
Randomizations will be done by computer. To achieve proper balance in the number of subjects per treatment, once a treatment reaches the target sample size, it will be excluded from the randomization.
Randomization Unit
Group of subjects at the session level.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
0
Sample size: planned number of observations
45 subjects * 4 treatments * 3 rounds = 540 observations
Sample size (or number of clusters) by treatment arms
45 subjects per each of the between-subjects treatments (4 treatments)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
With N=45/treatment we can detect a difference of at least d=0.3 in bids for a sigma = 0.7 and an Intra-class Correlation Coefficient across rounds of up to 0.3. Values for sigma and differences in bids are based on: Čagalj, Marin & Morawetz, Ulrich & Haas, Rainer. (2013). Willingness to pay for conventional and organic food products in Croatia.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Agricultural University of Athens Ethics Review Board
IRB Approval Date
2023-01-18
IRB Approval Number
04/18.01.2023
Analysis Plan