Question

A statistician wants to determine the average annual Gross National Product for countries in Africa. He samples the 20 largest (in terms of population) African countries over 10 years, and gets their quarterly G.N.P results for each quarter of each year. The statistician is criticized because the sample is not representative. Explain why.

Answer 1

The statistician wanted to determine the average G.N.P. for countries in Africa.

Some of the countries in Africa will have higher G.N.P while some will have low GNP.

The average GNP of the countries may vary or depend on several demographic parameters, population of the countries, being one of them.

So, to estimate the average annual GNP of countries in Africa the statistician should take a representative sample of the countries in Africa.

But he sampled the 20 largest African countries in terms of population.

This is a very biased sample. Since the average annual GNP of the countries in Africa may depend on the population size of the countries.

Thus, the sample that the statistician has taken us clearly non representative and biased.

So,he was criticized.