Everything else is ready: study the parts, the key terms and the quiz below.
Probability Basics
Reason about chance with outcomes, events and the rules that combine them.
In this lesson6 parts
- 01Name the recorded outcomes
- 02An event and its complement
- 03Overlap and addition
- 04Make the review decision
- 05What repeated draws can, and cannot, show
- 06Reproduce the counts and try another rule
Key terms
The words this lesson introduces, each in one line. The module’s glossary collects them all.
- outcome
- One possible result of the selection; here, one recorded transaction.
- sample space
- The outcomes under consideration; here, all 284,807 recorded transactions.
- event
- A specified set of outcomes, such as F, the 492 rows with
Class = 1. - empirical probability
- Event count divided by the recorded total: 492 / 284,807 = 0.173%.
- event A
- The rows satisfying a declared condition; here
Amount > 100, 56,508 rows. - complement
- Every outcome in the sample space outside an event.
- intersection, or joint event
- Outcomes satisfying both events: 130 rows above 100 and labelled fraud.
- joint probability
- Fraction of the sample space satisfying both events.
- union
- Outcomes satisfying at least one of the events: 56,870 rows.
- with replacement
- Each source label remains available for every draw.
- law of large numbers
- With repeated independent draws from the same distribution, a running fraction tends toward that distribution's probability.
Quiz 5 questions
Your first pick on each question is the one that counts, and a right one earns a coin. Getting one wrong here is how the lesson sticks.
Practice
Problems to solve in your own notebook. Each states the problem, not the steps: working out the steps is the exercise. Level A applies the lesson, B combines it with earlier ones, C stretches it.
The self-checking notebook for this lesson is Probability basics.
Common mistakes
What you will see when it goes wrong, why it happens, and the fix.
Where it’s used
Where this lesson’s ideas turn up in real work.