Table 1

The best formula for estimation by distribution.

Best Formula for Sample size (n)

Mean Estimation

Standard Deviation Estimation

Formula (5)

Median

Formula (16)

Range/4

Range/6

Log-Normal

n ≤ 23

23 <n

n ≤ 15

15 <n ≤ 64

64 <n

Beta

n ≤ 30

30 <n

n ≤ 15

15 <n ≤ 100

100 <n

Exponential

n ≤ 21

21 <n

n ≤ 15

15 <n ≤ 66

66 <n

Weibull

n ≤ 25

25 <n

n ≤ 16

16 <n ≤ 110

110 <n

Hozo et al. BMC Medical Research Methodology 2005 5:13   doi:10.1186/1471-2288-5-13