Find out if your proposed study has enough power.

Use the calculator below to see how these factors affect study power:

- Sample size: How many people are in your study?
- Exposed with disease: What percentage of those who were exposed developed the disease?
- Unexposed with disease: What percentage of those who where not exposed developed the disease?

To calculate study power, choose a value for each factor by moving the sliders with your mouse or entering numbers into the boxes above a slider and then pressing ENTER.

Sample Size |
Exposed with disease |
Unexposed with disease |
Study Power |
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people in the Exposed group of them developed the disease after exposure (1) people in the Unexposed group of them developed the disease without receiving exposure (2) |
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Assumptions Exposed must be greater than or equal to Unexposed Equal number of people in Exposed and Unexposed groups Level of significance is 5% or less Calculation is for a two-sample test for binomial proportions Sample Size must be large enough for this statistical test to be valid Calculator will only accept whole numbers as input |
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More Study Power is Better

More study power is desirable because this means that the proposed study is more likely to find an association between exposure and illness, if it exists. There is no set, specific value for study power that must be achieved in order to conduct a health study. However, researchers often want to make sure that their proposed study has at least 80% or 90% power. With that in mind, here is how to interpret the output from the calculator:

Calculated Study Power | Meter Color | Is This Study Power Acceptable? |

80% or Greater | Green | Probably Yes |

70% to 80% | Yellow | Probably Not |

Less Than 70% | Red | No |

N/A | Red | Your sample size is not large enough for the statistical test used in this type of study to be valid. Therefore, study power could not be calculated. |