My teacher explained the Central Limit Theorem and provided some examples. He told us that even if we don't have a normally distriuted variable, if we are working with sample means we can consider they are normally distributed (because of the CLT, and under the assumptions of: the samples have a large number of elements (typically larger than 30), the standard deviation and the mean of the population is finite).
But he applied it to a problem with the ages of people.
And I have a question. How can the distribution of the sample mean be normal if the age is always positive? The normal distribution is supposed have a domain from -inf to +inf.