Suppose you are trying to determine if the mean age of customers is 35 years old. You take a sample of 100 customers and find that the sample mean age is 28.

Based only on this information, what can you conclude about the population mean age?

Conclude that it is definitely not 35 because the sample mean is really “far away” from 35.
You cannot make a conclusion about the population mean based only on the sample mean. You need to conduct a statistical test taking into account sample size and standard deviation