Sample Size Calculator
 
Confidence Level: 95%99%
Confidence Interval (%):

Population size:
Do not use commas

Sample size needed:

Steps
1.  Confidence Level: Click desired level
2.  Confidence Interval: Enter %,  such as 4.9 or 5.0
3.  Population: Enter size if finite; otherwise, leave blank.
4.  Hit calculate button

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The confidence level indicates a degree of certainty (as a percentage) that that the results of a study fall within a given range of values.  Typical confidence levels are 95% and 99%.

The confidence interval (margin of error) is a plus-or-minus percentage that is a range within the confidence level.  For example, if a 5% confidence interval is used, and 50% of the sample gives a specific answer for a question, the actual result for that question falls between 45% and 55% (50 5).

When using confidence level and confidence interval together, researchers using a 95% confidence level with a 5% confidence interval can say that they are 95% sure their results are accurate within 5 percent.