Main Index> Basic Statistics>Difference Between a Statistic and a Parameter
A statistic and a parameter are very similar. They are both descriptions of groups, like “50% of dog owners prefer X Brand dog food.” The difference between a statistic and a parameter is that statistics describe a sample, whereas a parameter describes an entire population.
Alternatively, if you ask a class of third graders who likes vanilla ice cream, and 90% of them raise their hands, then you have a parameter: 90% of that class likes vanilla ice cream. You know this because you asked everyone in the population.
Here are some steps you take to be able to tell the difference between the two:
Step 1: Ask yourself, is this obviously a fact about the whole population? Sometimes that’s easy to figure out. For example, with small populations, you usually have a parameter because the groups are small enough to measure:
- 10% of US senators voted for a particular measure. There are only 100 US Senators, you can count what every single one of them voted.
- 40% of 1,211 students at a particular elementary school got below a 3 on a standardized test. You know this because you have each and every students’ test score.
- 33% of 120 workers at a particular bike factory were paid less than $20,000 per year. You have the payroll data for all of the workers.
Step 2: Ask yourself, is this obviously a fact about a very large population? If it is, you have a statistic.
- 60% of US residents agree with the latest health care proposal. It’s not possible to actually ask hundreds of millions of people whether they agree. Researchers have to just take samples and calculate the rest, so this is a statistic
- 45% of Jacksonville, Florida residents report that they have been to at least one Jaguars game. It’s very doubtful that anyone polled in excess of a million people for this data. They took a sample, so they have a statistic.
- 30% of dog owners poop scoop after their dog. It’s impossible to survey all dog owners—no one keeps an accurate track of exactly how many people own dogs. These data have to be from a sample, so it’s a statistic.
If in doubt, think about the time and cost involved in surveying an entire population. If you can’t imagine anyone wanting to spend the time or the money to survey a large number (or impossible number) in a certain group, then you almost certainly are looking at a statistic.