October rainfall in Samaru


If the rainfall distribution remains the same as in the past, we predict more than 57.4 mm rain in one out of every four Octobers.

Bootstrap simulation

Use this page to demonstrate bootstrap simulation — sampling with replacement from the actual data to build up the error distribution.

As in simulations from a normal model, click Accumulate and take several samples to build up the error distribution. (Note that the numbers refer to values that have been selected more than once.)

Click Estimate s.e. and bias to display the mean and standard deviation of the error distribution.

From either the complete error distribution or by applying the 70-95-100 rule to the standard error, our estimate of the upper quartile rainfall in October, 57.4 mm, is unlikely to be in error by more than about 20 mm.


Rainfall is highly seasonal in most of Africa and its timing and amount is critical for agriculture. This data set gives the rainfall in October of each year between 1928 and 1983 in Samaru, Northern Nigeria, between 1928 and 1983.

Annual rainfall in Samaru, Nigeria has a reasonably symmetric distribution, but rainfall in some months is very skew.