Delivering Prevention: Selling vs. Giving Reassessed

Last registered on June 29, 2021


Trial Information

General Information

Delivering Prevention: Selling vs. Giving Reassessed
Initial registration date
June 28, 2021

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
June 29, 2021, 10:29 AM EDT

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



Primary Investigator

University of Zurich

Other Primary Investigator(s)

PI Affiliation
University of Zurich
PI Affiliation
University of Zurich

Additional Trial Information

In development
Start date
End date
Secondary IDs
We conduct a randomized control trial experiment in Salima district, Malawi. This research project has four main objectives: i) to investigate how discounts affect take-up of different preventive health products, ii) to investigate how willingness to pay for different products varies with prior exposure to discount, iii) to investigate how price anchoring and learning influence future willingness to pay, and iv) to investigate how they might spillover to different types of goods.
External Link(s)

Registration Citation

Deambrosi, Maite, Jiajing Feng and Guilherme Lichand. 2021. "Delivering Prevention: Selling vs. Giving Reassessed." AEA RCT Registry. June 29.
Experimental Details


We visit poor households in Malawi offering different preventive goods at randomly assigned discounts. We further vary how price composition is framed: by randomizing what the delivery fee was, as part of that full price, households effectively pay different prices for the same good -- although with the same cash on hands by the end of that round. This generates variation in reference prices for the same good. We then revisit households a month later to elicit their willingness to pay for a range of preventive health care goods.
Variation in discounts for soap and multivitamins attempt to replicate previous empirical evidence. Variation in delivery fees allows us to study framing effects without affecting liquidity constraints, and minimizes concerns with experimenter demand effects for future demand. The distribution of experience and credence goods - soap and vitamins supplements, respectively - allows us to understand how anchoring and learning effects vary with the type of good.
Finally, eliciting willingness to pay for a larger set of goods, including experience and credence goods - allows studying the potential framing effects of discounts more broadly, understanding whether they spillover to other products.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
The key outcome variables that we are interested in measuring are the following:

- Willingness to pay in round 2 for a set of preventive health goods: soap, multivitamin supplement, mosquito bed nets, chlorine, waterguard, deworming tablets and Chiponde (supplementary feeding), conditional on treatment assignment in Round 2.

- beliefs about effectiveness of soap an multivitamin supplement in preventing diseases and in promoting child development.

- Children’s health measures,

- Recollection of phase 1: good offered, counter, and tag price.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We visit 3000 poor households in Malawi across 150 villages, offering different preventive goods at randomly assigned prices. The study will be conducted in two rounds.

In round 1, the survey team visits 150 villages that have been previously selected and, in all villages, randomly identifies 20 respondents meeting the sample criteria described in the previous section. The respondent is then assigned to one of 8 treatment groups determined by the cross-randomization of two conditions:

1. Counter price: total price (in Malawian Kwacha) for which the household can buy the product that is offered, inclusive of the delivery fee;
2. Tag price (in Malawian Kwacha): actual price of the good, that is, the difference between the counter price and the delivery fee.

The table presented in the attached Pre-Analysis Plan summarizes the treatment conditions and the sample composition.

By randomizing what the delivery fee was, as part of that full price, households effectively pay different prices for the same good -- although with the same cash on hands by the end of that round. Analogously to Chetty (2009), this variation in how the price of the good is framed, affects reference prices for those products, without influencing other important parameters determining future demand.
Moreover, within each cell, the type of good offered to participants is randomly selected. Half of the respondents will be offered an experience good, i.e. 3 bars of soap, while the other half will receive a credence good, that is a 100ml bottle of Multivitamin Supplement.

Once the individual has been selected, she is asked to complete a short survey (see next session) and is offered the possibility of buying soap or vitamin supplements - depending on which good is randomly selected - delivered to their doors at either full or discounted price, according to the table shown above. At the end of the visit, independent of whether the participant had decided to purchase the product or not, the enumerator reveals more information about the composition of the price, i.e. how much of the counter price that was paid covered the price of the product (tag price), and how much was the delivery fee.

In the second round, which takes place approximately 2-3 weeks after the first visit, the survey team revisits the same households and, before administrating a short survey, it elicits willingness to pay for a larger set of preventive health goods, which we categorize into "experience" and "credence" goods.

1. Experience goods: soap, mosquito bednets, chiponde (supplementary feeding).
2. Credence goods: multivitamin supplement, chlorine, waterguard, and deworming tablets.

To make our measure of willingness to pay as reliable as possible, we elicit it in an incentive-compatible way use the Becker-DeGroot-Marschak (BDM) mechanism. Moreover, the following measures are taken to mitigate all possible measurement concerns:

1. After being explained how the game works, households are asked to state their maximum willingness to pay to receive a single dose of each product, taking into account that delivery is offered for free during this second visit.
2. Only one predetermined good, namely soap, is actually sold in the end, but households learn which one only at the end of the experiment.
3. At the beginning of the procedure, each respondent is shown a unit of each good to make sure that they don't perceive some goods as more likely to be sold than others.
4. Given that respondent are likely to be unfamiliar with this type of game, we run a trial round with peanuts, to make sure that the rules of the game are clear before proceeding, and that participants understand that it's in their best interest to answer truthfully.
5. We randomize the order in which the goods are presented.
6. Finally, a price is randomly drawn and, if it is lower than the household's stated willingness to pay, the good is sold at that price. Otherwise, the household is not allowed to buy the product.
Experimental Design Details
Randomization Method
Our Randomized Controlled Trial is conducted across 150 villages in Salima district, Malawi.
Within each village, the survey team randomly selects 20 households to take part into the experiment. Our sample is built using a random walk approach: the enumerators assess the eligibility of every 5th or 4th house they encounter in the village while following a pre-determined path. If more than one caretaker is present in the household at the moment of the visit, one will be randomly selected to participate.

The households are considered eligible to participate in the experiment if there is at least one child aged 6 months to 12 years in the households.
Randomization Unit
All the treatment conditions (type of good, counter price and tag price), are randomized at the individual level.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
3000 individuals across 150 villages
Sample size: planned number of observations
3000 individuals across 150 villages
Sample size (or number of clusters) by treatment arms
Our design cross-randomizes three main treatment conditions:

- type of good delivered
- Counter price for the good
- Tag price

Each cell has 187 or 188 observations.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
The MDEs for our main questions are the following: - We are able to detect a 0.091 standard deviation effect for question 1 and 3, aggregating both types of goods, and a 0.128 SD effect when looking at good separately (question 2 and 4). For secondary research questions, the computed MDEs given our sample size are the following: - We are able to detect a 0.091 standard deviation effect for question 5 and 6, - We are able to detect a 0.148 standard deviation effect for question 7.
Supporting Documents and Materials

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Institutional Review Boards (IRBs)

IRB Name
Human Subjects Committee of the Faculty of Economics, Business Administration and Information Technology at the University of Zurich
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents

Delivering Prevention - Pre-Analysis Plan

MD5: 5eeaeb7ff9f3b5c3e4ff9a92124a8e49

SHA1: aa73749697eff2bbf78ad249339b587d57bbd967

Uploaded At: June 28, 2021


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