Natural Resource BiometricsSample Size DeterminationTo calculate the number of samples neededTo calculate the number of samples needed for a given error level use: where d = the desired absolute error in plus or minus of the units of measure, s = the standard deviation, t_{α} = Student's t value for n  1 degrees of freedom for the 1  α level of confidence, and n = the sample size. To calculate the error for a given number of samplesIf you have a set number of samples and want to know the absolute error use: where the variables are the same as above. To calculate the number of plots in relative termsTo calculate the number of plots in relative terms use the following formula: where the t and n variables are the same as above. c is the coefficient of variation in the percent form and E% is the desired error as a percent. Also See: Chapter 5  Sample Size Determination pages 173178 in:

Natural Resources Biometrics by David R. Larsen is licensed under a Creative Commons AttributionShareAlike 4.0 International License . Author: Dr. David R. Larsen Created: September 18, 2000 Last Updated: September 13, 2014 