SAMPLE SIZE CALCULATOR

HOW MANY PEOPLE SHOULD I MAIL?

Understanding how many people need to be contacted to ensure a statistically significant campaign result is one of the most common issues when planning a direct mail campaign.

Essentially, the answer depends on three key factors:

1. What response rate are you expecting?

This can be tricky if you don't have much experience running campaigns, but in the absence of campaign history consider using an industry benchmark figure.

2. What limit of error are you willing to accept?

You might like a 5% response rate, but would you be happy with 0.5% either side of that (ie: a result within the range of 9.5% to 10.5%)? This is your limit of error.

3. How confident do you want to be in the result?

Obviously, there can't be a 100% guarantee that if you repeat the campaign you'll get the same result, so generally a confidence level of 95% is advisable - meaning you're likely to get the same result 95% of the time. You may find that you need to reduce the confidence level on some occasions in order to make the test viable.

This tool will help you in planning your campaign but remember that nothing is a better guide to success than previous learnings, which is why testing is so valuable in direct marketing activity.