We regret that three errors occurred in the previous paper in the series “An introduction to statistics” (Driscoll P, Lecky F, Crosby M. Article 4. An introduction to estimation—1. Starting from Z.).

On p 413 the key point, 1st column, should read:

SEM = Population standard deviation (σ)/√number in the sample (n)

On p 414, 1st column, the 1st and 2nd lines should read:

SEM = Population standard deviation (σ)/√size of the sample (n)

On p 415, 1st column, the 2nd sentence should read:

As the latter is equal to the √(σ)/n, the range can only be reduced by increasing the sample size.