Definitions

Data

A piece of “data” is just a thing you know and wrote down. Someone’s name. The height of a giraffe. The temperature in Tulsa, Oklahoma at 3pm on July 19, 1987. You get it.
The word comes from Latin datum: that which is given. Facts.
So, data is “stuff we know already”. When a researcher goes to “gather data,” they are going out to find new facts and information to record (and later, study).

Variable

A “variable” is some kind of information you have on each of the “things” you are studying. So if we are studying penguins, a variable might be “species”. Some penguins are from the “Adelie” species, some are “Gentoo,” some are” Chinstrap,” etc. That is, the value of “species” will vary among penguins. Another variable could be “body mass” - again, each individual penguin has their own body mass, so “body mass” varies across penguins.
Note: In writing computer code, a “variable” means something slightly different. We’ll talk more about this in the tutorial portion.

Numerical Variable:

A variable where the values are numbers with real quantitative meaning(see below).

Categorical Variable:: Anything that is not numerical. Each unique value is called a level (see below).

Continuous Numerical Variable: - Values can take any decimal number, though possibly in a restricted range.

Discrete Numerical Variable:: A numerical variable that takes values that have jumps between them.

Nominal Categorical Variable

A categorical variable with levels with no natural order.
“Name” is a good one. OK yes, often we order them alphabetically when we make a list of people, but that’s just to it easier to read. It’s not really true that the name “Alice” is “less than” the name “Bob.”

Ordinal Categorical Variable

A categorical variable with levels that have a natural order.
For example, a company might sell a T-shirt in three sizes: small, medium, and large. You can’t really average a bunch of t shirt sizes, but “small” is definitely less than “medium,” which is definitely less than “large.”

Data Frame

An table that associates the observations (rows) with the variables measured on each observation (columns).

Unit of Observation

The “things” we are studying. If it’s a true dataframe, each row is exactly one observation. So the “unit of observation” is just “what does a single row represent?”

Summary: A numerical, graphical, or verbal description of an aspect of data that is on hand.

Generalization: A numerical, graphical, or verbal description of a broader set of units than those on which data was been recorded.

Causal Claim: A claim that changing the value of one variable will influence the value of another variable.

Prediction: A guess about the value of an unknown variable, based on other known variables.