Solved – Determining market share from multiple choice questions on a survey

survey

Say, for example, that I want to determine the market share or relative popularity of coffee houses within a certain population through a survey. What is the best way to write a question that accurately measures this?

Some issues that I am thinking of:

I don't want to ask a single choice question ("Which coffee house do you go to?"), because the coffee houses are not mutually exclusive. I may enjoy more than one equally often.

If I ask a multiple choice question, then I can't really get a real "market share," since the sum of the proportions of people who go to each coffee house sum to over 100%. I can only say that "x% of people in this population go to this coffee house."

Is it possible to ask a series of questions ("Which coffee house do you prefer the most?" "Which coffee house do you prefer the second most?", or "Rank the following coffee houses")?

Can I ask a multiple choice question then rebase the proportion to the total number of responses? For example, if I have 100 respondents, but they selected 200 coffee houses (because each respondent said they went to two coffee houses, maybe), can I calculate a frequency table based on 200, the number of selections, instead of the number of respondents?

Best Answer

I'd suggest several Qs along these lines:

  1. Which is the one coffee house you go to most often?
  2. What other coffee houses do you visit more than once a month (say)? [Probe to negative, i.e. keep asking ".. and which others do you visit more than once a month?" ".. and which others?" until interviewee answers "none"/"that's it" / "no others" ]
  3. What other coffee houses can you recall having ever visited? [Probe to negative]
  4. [For each coffee house mentioned in (1) or (2)]: "How many times have you visited Cafe Y in the last month?"

Tabulating responses to (1) gives "X% of people said they go to Cafe Y most often" for each Y, with sum <=100% (can be <100% as some people never visit coffee houses).

Combining responses to (1) & (2) gives "X% of people go to Cafe Y more than once a month" for each Y, with sum > 100% but still with denominator N for each coffee house, where N is number of respondents. Similarly combining (1), (2) & (3) gives "X% report ever having visited Cafe Y".

Taking the mean of (4) for each coffee house gives you "Cafe Y was visited an average of m times in the preceeding month". Denominator is N again (remember to include those respondents who didn't mention Cafe Y as zeroes).

In principle you could refine things further, but asking more Qs that this may increase your respondent quit rate.

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