Sample Size Calculator
This sample size calculator will tell you how many completed surveys you need for your project to ensure that your total target population is accurately represented. Before you calculate this number, you should be familiar with the key terms defined below:
CONFIDENCE LEVEL – the probability that your sample accurately reflects your total target population, expressed as a percentage. If you select a 95% confidence level (the industry standard), you are declaring that if you repeated the survey you would get the same results 95% of the time.
MARGIN OF ERROR – also called a confidence interval, measures the percentage of the total population that may deviate from your received responses. The industry standard margin of error is 5%. It is typically indicated with a plus-minus sign (ex: +/- 5%).
POPULATION SIZE – The total target population (e.g, all people in the U.S. who have health insurance). NOTE: If this number is too large or unknown, you can leave this field blank; the calculator will default to the highest population threshold.
Example: Acme Company surveys its customers and finds that 60 percent of the respondents say its customer service is “very good.” The confidence level is cited as 95 percent plus or minus 5 percent. This means that if the survey were conducted 100 times, the percentage who say service is “very good” will range between 55 and 65 percent (95 percent of the time).