Reference Range Calculation using Normal Distribution

Online calculator which helps to estimate the lower and upper limits of the standard reference range (also known as reference interval) based on normal distribution.

Estimate Lower, Upper Limits of Reference Interval


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Lower Limit = m - t0.975,n-1 x √((n+1)/n) x s.d Upper Limit = m + t0.975,n-1 x √((n+1)/n) x s.d Where, t - Distribution. s.d - Standard Deviation n - Total Count m - Mean

97.5% percentile with (n-1) degrees of freedom corresponds to t0.975,n-1 from the Student's t-distribution table.

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