Organ Donation

Organ Donations

• While a majority of people approve of organ donation in principle, far less than that actually sign up when getting a driver’s license.
• Different states have different recruiting methods.
• Do these different methods result in different sign-up rates?

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From Do Defaults Save Lives (2003) https://www.science.org/doi/10.1126/science.1091721

STEP 1: Ask a research question

• In general: Is there a method that will increase the likelihood that a person agrees to become an organ donor.
• More specifically: Does the default option presented to driver’s license applicants influence the likelihood of someone becoming an organ donor?

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STEP 2: Design a study and collect data

• Recruited participants from general interest internet bulletin boards
• Each was asked to pretend to apply for a new driver’s license.
• Participants did not know in advance that different question phrasings were given for the donor question, or even that this issue was the main focus of the study.

STEP 2: Design a study and collect data

• Participants were given one of three different question versions regarding organ donation:
• Choose to be a donor or not, without being given a default option (the “neutral” group, Michigan’s current practice).
• Told the default option was not to be a donor but that they could choose to become a donor if they wished (the “opt-in” group, California and Arizona).
• Told that the default option was to be a donor but that they could choose not to become a donor if they wished (the “opt-out” group, some countries use this practice).

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STEP 3: Explore the data

42% v. 82% v. 79%

Step 4: Draw inferences beyond the data

• 3S Strategy:
• Statistic: what statistic can we use to measure the differences among the groups?

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42% v. 82% v. 79%

Mean Group Difference:

Step 4: Draw inferences beyond the data

• 3S Strategy:
• Simulate: What sorts of values for the Mean Group Difference can we expect just by random assignment alone?
• Imagine you have a stack of index cards – how many?
• What to write on each card?
• Shuffle deal into ____ groups with _____ in each group

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Recompute the Mean Group Diff and plot the value

Step 4: Draw inferences beyond the data

Step 4: Draw inferences beyond the data

Based on a very small p-value < 0.001 we have strong evidence the type of question phrasing has an effect on choice to be an organ donor. This conclusion applies to people similar to those in the study, under similar conditions.

Step 4: Draw inferences beyond the data

• From the authors of the study:
• Reported strong evidence that the neutral and opt-out versions do lead to a higher chance of agreeing to become a donor, as compared to the opt-in version currently used in many states.
• In fact, they could be quite confident that the neutral version increases the chances that a person agrees to become a donor by between 20 and 54 percentage points, a difference large enough to save thousands of lives per year in the United States.

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Step 5: Formulate Conclusions

• Based on the analysis of the data and the design of the study, the researchers concluded that the neutral version causes an increase in the proportion who agree to become donors over the opt-in.
• But because the participants in the study were volunteers recruited from various general interest Internet bulletin boards, generalizing conclusions beyond these participants is only legitimate if they are representative of a larger group of people. (The authors believed their sample included a “broad range of demographics.”)

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Step 6: Look back and ahead

• One limitation of the study is that participants were asked to imagine how they would respond, which might not mirror how people would actually respond in such a situation.
• A new study might look at people’s actual responses to questions about organ donation or could monitor donor rates for states that adopt a new policy.
• Researchers could also examine whether presenting educational material on organ donation might increase people’s willingness to donate.
• Another improvement would be to include participants from wider demographic groups than these volunteers.

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Theory-based test

• Chi-square test
• Ho: There is not an association between question phrasing and choice to be a donor in the long-run
• Ha: There is an association between question phrasing and choice to be a donor in the long-run

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If Ho is true, what will the segmented bar chart look like for the percentage of donor/not donor in each question phrasing group?

Theory-based test

• Chi-square test
• Ho: There is not an association between question phrasing and choice to be a donor in the long-run
• Ha: There is an association between question phrasing and choice to be a donor in the long-run

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If Ho is true, what will the segmented bar chart look like for the percentage of donor/not donor in each question phrasing group?

Theory-based test

• Chi-square test
• Ho: There is not an association between question phrasing and choice to be a donor in the long-run
• Ha: There is an association between question phrasing and choice to be a donor in the long-run

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Recruiting Organ Donors