Why you should be careful when averaging percentages

A common mistake I often observe in data analysis is the averaging of percentages. To explain this concept let’s examine a simple example. Suppose we conduct a survey on whether people like or do not like chocolate. We discover that 90% of children like chocolate; however, only 60% of adults like chocolate. So, can we claim that 75% of the population ( average = (90%+60%)/2 = 75% ) like chocolate? The answer is NO! There is one exception which we will discuss at the end