Determination of Sample Size from a pilot study is the easiest way of determining sample size for Your study. In this type of sample size determination 3 values can be obtained from the sample size taken from pilot study.

1) Standard Error of Mean (2) Precision (3) Sample Size

The Formula Used for This type of Sample size determination is

N = (Z α2) X SD2/ Precision2

Z α– Statistical constant (1.96)

SD – Expected Standard Deviation (that can be obtained from previous studies or a    pilot study).

d – Precision/ allowable error (corresponding to effect size)

Remember following general Guidelines while trying to determine sample size from a pilot study.

1. Use the pilot study which deals with the same topic as of yours. Like for example if your study is about neonatal seizures then pilot study must also deal with neonatal seizures.

2. Use the pilot study in which number of cases are near to the number of cases you want to include in your paper. For example, if you want to include 80 cases in your study then use pilot study in which close to 80 patients has been included.