Statistics problem about large samples and normal distribution

Question

A researcher has collected a large sample of IQ scores from his friends and relatives. He claims that because his sample is large and the distribution of his sample scores is very close to the bell shape of a normal distribution, his sample is representative of the population.

Is this reasoning correct?
Why or why not?

Answer 1

This is not correct reasoning.  In order to be representative of the population it must be the case that any individual from the population had the same chance of being in the sample.  But individuals who were not friends or relatives of the researcher had zero chance of being in the sample.  So this researcher's sample is only representative of his friends and relatives, not of the whole population.