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Sample size calculation: Correlation coefficient

Command:Sample size
Next selectCorrelation coefficient


Calculates the required sample size for a correlation coefficient. The sample size takes into account the required significance level and power of the test (see Sample size calculation: Introduction).

Required input


For example, the correlation coefficient between two variables is thought to be 0.60. How many patients are required for this correlation coefficient to be significantly different from 0.0?

For α-level you select 0.05 and for β-level you select 0.20 (power is 80%).

Sample size calculation for correlation.

After you click Calculate the program displays the required sample size (19 in the example, meaning that you will need 19 cases in which both variables must be measured).

A table shows the required sample size for different Type I and Type II Error levels.


See also

Recommended book

Book cover

An Introduction to Medical Statistics
Martin Bland

Buy from Amazon

This textbook is intended for medical researchers and includes the design of clinical trials and epidemiological studies, data collection, summarizing and presenting data, probability, standard error, confidence intervals and significance tests, techniques of data analysis including multifactorial methods and the choice of statistical method, problems of medical measurement and diagnosis, vital statistics, and calculation of sample size.