Statistics allow us to determine laws in otherwise random world. Things happen with some level or randomness (error term in statistics). If you get A from a single math test and your friend gets a B, you would probably say it can be due to chance. But if you get an average of 85 points over 5 tests whereas your friend gets 77, you might start to think you are just better at Match. BUT that is your opinion, not a proof. It can all be due to some level or randomness in teachers evaluation or your own performance fluctuation. Statistical tests will estimate these fluctuations (standard deviation) and then asses if the difference in scorese (85 vs 77) can be explained just by these random events or if it is more likely there is an underlying difference in your Math skills.
We can separate our numeric data into continuous vs discrete.
Categorical variables come in two forms: nominal and ordinal. We have no way to “sort” nominal data, but we can sort ordinal data - income level, finishing position in a race.
Favorite color or meal, gender
Ratio data are
Type I error: Type II error: