There’s no question survey data is a powerful asset for virtually any business. To get the most effective results, however, a lot goes into creating and running these surveys. Getting your survey questions, the polling tool you choose, and your survey sample size are just a few of the factors to consider for getting it just right.
Considerations for Determining Survey Sample Size
Today, we’ll focus specifically on survey sample size to provide you with four key considerations to keep in mind for your own surveys based on your goals and your organization. There’s often a fine line between your survey sample size being too small, too big, or just right. But when you consider these four points, you give yourself the best chance at getting survey sample size down to an art.
Total population size of your target group
In some cases, determining the total population size to use for calculating your survey sample size is pretty straight forward.
For example, let’s say you want to poll dog groomers about their business practices. A quick Google search tells you that as of 2017, there were approximately 189,384 dog groomers employed in the United States. This gives you a good idea of the total population size of your target group. You will want to focus on getting a certain proportion of that total audience to ensure you’re getting an accurate picture from survey results. If only 100 dog groomers take your survey, their responses don’t necessarily reflect the majority of all dog groomers.
So, start with the total size of your target audience, and this will give you a better idea of how many people who need to poll for the most accurate results.
Margin of error
Virtually every survey or poll needs some margin for error. You can’t always count on respondents being completely honest in their responses, for example. To work around this, you will need to determine the margin of error that is acceptable for your survey. This plays into the total survey sample size because the margin of error may be bigger if you’re polling a larger audience.
The margin of error is also referred to as the confidence interval. Generally speaking, with a larger margin of error, there tends to be less confidence in the results. Take a look at this page next to learn more about calculating the margin of error and how to interpret your results based on the results.
(While we’re on the subject of surveys, here’s another post you might like to read next)
Although they’re often confused for one another, confidence level and confidence interval are two different things. In this case, confidence levels just means how confident you can be in your results. Confidence level is represented as a percentage, and this percentage indicates what percentage of your survey’s target audience would choose an answer within the margin of error. Most surveyors use 95% as their confidence level, but others opt for 90% and some for 99%.
And now for the final consideration to take into account when you’re determining your survey sample size: standard deviation. Think of standard deviation like this: If you ask respondents to vote on a scale of 1-10, and every response is either five or six. Because the numbers don’t range much, the standard deviation is small. However, if responses ranged from 1-10, there’s a higher standard deviation.
Calculating Your Survey Sample Size
Now, we’ve covered four key calculations to help you determine your survey sample size. But what about calculating your survey sample size itself? To do so, the formula looks like this:
z is the z score
ε is the margin of error
N is population size
p̂ is the population proportion
(Chart resource: Sample Size Calculator)
If that formula gives you nightmare flashbacks to algebra class, don’t panic! Luckily, there are plenty of free, user-friendly tools to help you get the job done rather than breaking out a pencil and paper.
Head over here to Calculate.net where you can quickly enter your stats and figures and calculate your survey sample size in just a few clicks. In addition to the sample size calculator, you’ll also find a standard deviation calculator, a margin of error calculator, and a number of other helpful tools.
Ready to get out there and start creating your own polls and surveys? Swift has all the tools you need to get the job done! Whether you want to run an SMS poll, a live poll, a web poll, a Q&A session, or more, you’ll find everything you need in our suite of audience engagement tools.