# Sample Size for Population Survey

Menu location: **Analysis_Sample Size_Population Survey**.

This function gives you the minimum number of subjects that you require for a survey of a population for the proportion of individuals in that population displaying a particular factor, with a specified tolerance (Colton, 1974; Feinstein, 2002).

__Information required__

- cc: confidence level (1-alpha, where alpha is the two sided probability of detecting a false effect: double alpha if you need a one sided estimate).
- N: population size.
- p%: estimate of rate (as a percentage) at which characteristic occurs in the population.
- d%: absolute deviation from p% that you would tolerate (i.e. p% give or take d%).

__Technical validation__

The estimated sample size n is calculated, using simple Gaussian theory, as:

- where p is p%/100, d is d%/100, and z is a quantile from the standard normal distribution for a two tailed probability of 1-cc. n is rounded up to the closest integer.