Unit 14
Probability.
Counting outcomes with a tree and a table, probability as a fraction, combined events, and why many tosses form a bell.
Before this unit
The unit, lesson by lesson
Lessons
4 lessons · 19 practice questions · about 2 hours
Counting outcomes
Before talking about chance, count what can happen. A tree of choices, the multiplication principle, every outcome of two dice, and how many orders a few books can stand in on a shelf.
Chance as a fraction
When every outcome is equally likely, a probability is the fraction of all the outcomes that fit. Why a total of seven with two dice is six times as common as a total of two, and the chance that something does not happen.
Or, and, not
How events combine. At least one six with two dice through the complement, why you cannot add the chances of events that can happen together, when you multiply, and why a coin has no memory.
The bell curve
A Galton board is many coin tosses in a row. How many paths there are, why most balls land in the middle, what moves when the pegs are not fair, and why the average result is not the result you usually get.