The sample size, or number of people you need to complete your survey, depends on two factors – how big is the population and how confident do you want to be in the results.
Most people are surprised to find out that the number is smaller than they anticipated. I was working for a young company in Estonia and we had recruited a local market research agency to track our brand progress. Being ignorant about market research we were ever suspicious about the fact that they were drawing conclusions from a nationally representative sample size of 1000.
The sample size of “only” 1000 people simply didn’t feel big enough to make authoritative claims for the whole population of a whopping 1.4 million people.
The better news – it’s easy to figure out the sample size needed for your survey. All you need to know is the target population size – the number of people relevant to your study.
Couple of tongue-in-cheek examples:
|Population||Required sample size|
|528 - people who have been to space||223|
|10,490 - athletes at the London 2012 Olympic Games||371|
|110,000 - wine growers in France||383|
|5,300,000 - all Hebrew speakers||384|
|50,000,000 - everyone who’s bought Michael Jackson’s "Thriller"||384|
|1,344,130,000 - everyone in China||384|
Hang on! Why are some surveys then conducted with panels in the tens of thousands? Two main reasons:
An example of the latter: A study among iPhone users asks "Have you used in-app purchases?" and those who answer "Yes", are required to answer 5 more questions on the topic. If you started with 400 respondents then maybe half will answer those extra questions. Will 200 responses still give you valid data?
There are easy to use sample size calculators available on the internet but this table below gives a pretty good overview to kick things off.
It's always good to consult with an expert if in doubt. Our client services team is always happy to help out when it comes to mobile-specific research, sampling questions etc. Just get in touch »