Table 2.
Measures of participant comprehension of risk probabilities
| Question ID/type and difficulty | Question | Answer format |
|---|---|---|
| Q1/Carrier risk (easy) | What do you think the probability is that John is a carrier of cystic fibrosis? You can indicate this probability as a percentage, or in another way if you prefer. | Free text |
| Q2/Carrier risk (easy) | Please indicate the probability that John is a carrier of cystic fibrosis by dragging the slider below.a | Probability slider from “0% chance” to “100% chance” |
| Q3/Risk to child (easy) | If John and Jane have a child, what do you think the probability is that the child will have cystic fibrosis? You can indicate this probability as a percentage, or in another way if you prefer. | Free text |
| Q4/Risk to child (easy) | Please indicate the probability that the child will have cystic fibrosis by dragging the slider below.a | Probability slider from “0% chance” to “100% chance” |
| Q5/Risk to child (hard) |
Imagine that there are 1000 couples in exactly the same situation as John and Jane: that is to say, • one partner is a carrier (like Jane is), and • the other partner has had the same test that John has had, and received the same result as John did. If each of these 1000 couples have one child, about how many of these 1000 children would have cystic fibrosis? If you aren’t sure, or if you think there are many possibilities, please make your best guess as to themost likely number of children to have cystic fibrosis, from 0 to 1000. |
Free text; single number expected |
| Q6/Risk to child (hard) | [As above with “800” in place of “1000”] | Free text; single number expected |
| Q7/Both risks |
• Which of the following possibilities is more likely? • John Doe is a carrier of cystic fibrosis • The first child of John and Jane Doe will have cystic fibrosis |
Multiple choice: • It’s more likely that John Doe is a carrier of cystic fibrosis • It’s more likely that the first child of John and Jane Doe will have cystic fibrosis • Both possibilities are equally likely • Don’t know |
aThe following text followed in both cases: “If you aren’t sure, please make your best guess. If you can’t mark exactly the probability you want using the slider, please put it as close to that probability as you can.”