Why is sample preferred to population?

Answer 1

Sample is preferred to population because observing the population can be impossible due to its size. You take a random sample of the population and, with statistics, you can infer things about that population to various degrees of confidence based on the sample size and on other knowledge about the population. For instance, if you wanted to know how many people on earth have brown hair, you would not check all 6 billion people - you would create a sample set, say a few hundred, thousand, or whatever - count the number with brown hair - and then run your calculations.