This provides a quick and simple estimate of standard deviation. Providing your data approximate to a normal distribution, their population standard deviation (σ) can be estimated from the range.
Algebraically speaking 
σ_{} = Range × multiplier_{(n)}
where :
 σ is the estimated standard deviation,
 the range is the maximum  minimum
 the multiplier_{(n)} is looked up in the appropriate table for that number of observations.
Table 1 gives the values of the multiplier for n = 1 to 1000.

Let's work this out for our lamb PCVs
Worked example
Lamb No.  PCV 
1  33 
2  26 
3  29 
4  32 
5  31 
Range  3326 = 7 
We will assume the data follow a normal distribution.
The range estimate of the standard deviation (σ) is therefore:
Range Estimate of σ 
= 
Multiplier_{n=7} × Range 

= 
2.59 
Τhis compares with a value of 2.95
using the corrected average of the sum of the squared
deviations from the mean.
The range estimate provides a quick and easy way to check the
standard deviation when calculated in the conventional way.
For small sample sizes (n<10) the range estimator is
surprisingly efficient (>85%). Efficiency in this
sense means that to get the same accuracy for s calculated when
n=10, we would have to use a sample size of 12 for the range
estimator. Hence the efficiency is approximately 10/12 or 85%.