I wish I had a dollar for every time a survey was administered asking people to rate their frequency of some behavior. The unit of measurement is often unclear in questions about frequency, like this one:
Q: How frequently did you visit the post office in the past 30 days?
__ Very frequently
__ Somewhat frequently
Here is what two respondents thought when they read the question:
Ryan: “I had to go there three times this month because they lost my package. That’s too many times. I’ll say very frequently.”
Miriam: “I go there three times a month to pick up stuff from my husband’s post office box. That’s just our system, so I guess that means somewhat frequently.”
In this question, the word frequently is not well defined. They both went three times in the past 30 days and gave different responses!
Stating a specific unit of measurement (in this case, the number of visits) will make the question clear.
Q: How many times did you yourself visit the post office for any purpose in the past 30 days?
______ # times visited post office in past 30 days
This version of the question does not ask respondents to interpret what we mean by frequently and we actually know what the respondents mean.
If we wanted to know perceptions of frequency, we could then ask about whether they consider 3 visits a month frequent or infrequent.