The difference between a sample statistic and a population parameter is that the sample statistic represents the sample that was actually studied, and the population parameter describes the entire population the sample represents. Your sample statistic allows you to make an inference about what the population parameter might be. For example, if you wanted to measure how many five-year-olds believe in Santa Claus, you would need to find a sample of five-year-olds to study since you cannot study them all! If you find that 75% of the children you studied believe in Santa Claus that is a sample statistic. From this we can estimate that approximately 75% of five-year-olds believe in Santa Claus.