Chapter 10
Data, Counting, and Probability
Thirty test scores come back, and someone asks how the class did. Reading all thirty aloud answers nothing. Until now, every number you have worked with described one definite thing, but a class is thirty things at once, and tomorrow's weather is not settled at all. Even so, both questions get answered every day, with a class average or a chance of rain. A single number can speak for a whole crowd of numbers, and even for an event nobody can predict. How far can a number like that be trusted?
What You'll Explore
4 lessons.
- Mean, Median, Mode, and Range
Suppose seven friends compare how long their walk to school took. Six took about ten minutes and the seventh took nearly an hour. Which single number honestly describes that group? You will meet several different ways to name a center, see them disagree with each other, and ask what a center alone cannot tell you.
- Reading Data and Graphs
One bar looks twice as tall as the one beside it, though the numbers behind them are nearly equal. A picture of data can make a fact obvious or make a small difference look enormous. This lesson goes through the common displays, what each is built to show, and what to check before you trust one.
- Basic Counting Principles
How many different outfits come out of six shirts and four pairs of shoes? You could write out every one, and with small numbers that works, but the list grows fast. This lesson looks for a way to know how many possibilities there are without ever listing them.
- Introduction to Probability
Nobody knows which face a die will land on, yet everyone agrees that a six is less likely than an even number. Vague words like likely and unlikely can be traded for numbers on a fixed scale, and this lesson asks where such a number comes from, and what happens when you actually roll the die many times.