Find out how to accurately work out your online survey sample size. How many survey invitations should you be sending and how to you know the number of responses that will make your data statistically significant? Get the important information you need NOW, with Obsurvey's FREE 30 day trial: http://blog.obsurvey.com/go/SSST/

1. Survey Invitations,
Sample Size &
Statistical Significance

2. You need to get enough
completed surveys back so
that it accurately represents
your population as a whole.

3. Here is a simple guide to calculate
sample size and how many
people to send your survey to…

4. Population Size
Determine what your whole population size is.
Your population is the entire set of people you
want to study with your survey.

5. Confidence Interval
(margin of error)
Accuracy that responses received represents
the views of population.
This will be your margin of error.
A standard confidence interval is 5% (up to
10%).

6. Confidence Level
(accuracy)
How accurately your sample represents your
population.
95% confidence level means you would get the
same results 95% of the time even with different
population samples.
Not advised to go below 90%.

7. Sample Size
Number of completed responses you need to
get back.
Different from the number of people you need
to invite.
Not everyone that you send your survey to will
necessarily complete it.

8. Response Rate
Won’t know your response rate until after you
send out your survey
Need to use a little bit of guesswork
Good recommendation would be to have a
response rate estimate of 10-15% (conservative
percentage)

9. So, how many people do you
need to send your own survey to?

10. Sample Size
÷
Response Rate

11. For example,
A sample size of 200 and an
estimated response rate of 10%,
would be this calculation:
200 / 0.10 = 2000

12. In other words,
10% of 2000 = 200
Which is your required sample size.

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