Suppose you are trying to determine if the yearly income of workers in a given area is the same in 2015 than it was in 2014, on average. You take a sample of workers and measure the yearly income in both years for each member of the sample. You find that the sample mean of the 2014 incomes was $26,078 while the sample mean income of the 2015 incomes was $27,402.

What can you conclude about the population mean yearly incomes in the two years?

Conclude that the population means are different because the sample means are different.
You cannot make a conclusion about the population means based only on the sample means. You need to conduct a statistical test.