The document presents a formula for calculating sample size in statistical tests, denoted as n = n1 = n2. It includes components such as zα/2 for significance, zβ for power, σ2 for population variance, and the minimum important difference (μ2-μ1). The formula allows for the estimation of sample size based on previous studies or calculated values.

1. Formula N = n1= n2 = (Zα/2+ zβ)2 x2σ2
( µ2-µ1 )2
Where Zα/2 = normal distribution value at α/2 level of significance
Zβ = normal distribution value at (1- β )power of test
σ2 = population variance of outcome variable under study which can be assumed from the
studies or as( max-min)/6.in case from any previous studies µ2-µ1=MID (minimum
important difference ) is available, the same can be used