Welcome to Really Simple Statistics (RSS). There are lots of places online where you can ponder over the minute details of complicated equations but very few places that make statistics understandable to everyone. I won’t explain exceptions to the rule or special cases here. Let’s just get comfortable with the fundamentals.
What? There are different kinds of Numbers?
In statistics, the type of number you use determines the type of statistic you can use. Learn these and you’ll have an easier time deciding what statistic makes more sense to use. There are four basic types of numbers that we consider in statistics.
What are Nominal Numbers?
Nominal numbers make the least sense because they aren’t really numbers. Nominal numbers are simply numbers that are different. 1 is not 2. 3 is not 9. It really makes more sense to think of things like apples and oranges, or cookies with green sprinkles vs cookies with red sprinkles. There is no reason to assign apples to the number 1 or 3 nor does it make any sense to assign oranges to the number 2 or 9. We just assign numbers to things because it makes doing statistics and creating charts easier. It’s like a check all that apply question on a survey.
cooee from morguefile; mensatic from morguefile
What are Ordinal Numbers?
With ordinal numbers, we have a little bit more information about the numbers. When we use ordinal numbers, we know that one of the numbers is bigger than another number. We know that 2 is bigger than 1, and 7 is bigger than 3. And it works the other way too. 1 is smaller than 2 and 3 is smaller than 7. We know which number is bigger, we just don’t know by how much bigger. One cookie is simply bigger than the other cookie. And I’ll have the bigger one. Like you could even yank it out of my hand. These types of numbers show up when we use Likert scale questions on a survey.
What are Interval Numbers?
Now let’s add in another piece of information. Interval numbers tell us everything we learned above, AND they tell about the spacing between the numbers. For instance, the amount of space between 1 and 2 is the same as the amount of space between 6 and 7. Or, the difference between 1 and 2 cookies is the same as the difference between 2 and 3 cookies. The difference in both cases is exactly one cookie. My cookie.
What are Ratio Numbers?
And lastly is where we thank Muhammad ibn Ahmad al-Khwarizmi. Ratio numbers incorporate the number zero. Now we know which number is bigger, and we know how much bigger, and we also know how to create none of it. This would be a survey question where you ask people to make sure their numbers add up to 100%. But I don’t dare illustrate what zero cookies looks like. The shock of it might kill me.