Patient-Reported Outcomes

4. Individualized Quality of Life Measures

Exercise 4

Which set of questions would be more amenable to an item response theory approach?
Click on the table you think is the correct set of questions.

Table A. Question on Vision

  • Can you see clearly enough to drive at night?
  • Can you see clearly enough to drive during the day?
  • Can you read fine print?
  • Can you read the newspaper?
  • Can you see clearly watching television?
  • Does vision make it difficult for you to cook?
  • Can you recognize people when they are close to you?

Table B. Question on Feelings

  • Do you often feel sad?
  • Do you often feel anxious?
  • Are you often worried?
  • Do you sometimes feel happy?
  • Do you have difficultly concentrating?
  • Do you have difficulty sleeping?

Correct Answer: Table A is more amenable to item response theory because it includes a clearly ordered set of questions. For example, the series of questions starts with a broad concept of driving at night, to a more focused response of recognizing faces close up. Each question asks about vision from distance to close up. Unidimensionality might happen in that if you can read fine print, you should be able to read the newspaper, see clearly to watch television, etc.

Incorrect: Table B contains items with many different concepts that are unlikely to form a unidimensional scale when analyzed by Item Response Theory.