Basic Formulas For Sample Size. You have to increase confidence or increase error reduce precision or both. 2 select the type of study design.
N Population size Z Critical value of the normal distribution at the required confidence level p Sample proportion e Margin of error. The sample size is denoted by n or N. Rule of Thumb The basic formula is n 16 2.
In calculating the sample size we are interested in calculating the population parameter.
We should know that the sample size we are taking from the population will not hold good for the whole sample. There are many formulas available which can be applied for different types of data and study designs. As stated previously we normall approximate 196 by 2. Some researchers follow a statistical formula to calculate the sample size.
