### Sample size calculation : Single group cohort

**Minimum sample size required can be calculated using the formula:**

μ0 = population mean

μ1 = mean of study population

N = sample size of study population

σ = variance of study population

α = probability of type I error (usually 0.05)

β = probability of type II error (usually 0.2)

z = critical Z value for a given α or β

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Suppose, the mean outcome of an intervention is 265 and SD is 9 and the expected mean of outcome of the study is 260. Using alpha as 0.05 and beta as 0.2.

N = 25 (using the formula above)

Source: https://clincalc.com/stats/samplesize.aspx