Chapter 18

Statistics and Probability

Statistics is the mathematics of real-world events. In statistics, you analyze data sets — information measured from actual events — using a variety of tools. Probability measures the likelihood of an event whose outcome is unknown. Calculating probability rests upon ordered methods of counting possible outcomes of events. In this section, you solve problems in both statistics and probability.

The Problems You’ll Work On

Here are the main skills you practice in the following problems.

Finding the mean, median, and mode of a data set

Calculating a weighted mean

Counting independent and dependent events

Deciding the probability of an event

What to Watch Out For

Here are some tips for calculating statistics and probability in the problems that follow:

When a question asks for the average without specifying which type, calculate the mean using the following formula: .

To find the median, rank all values in the data set from least to greatest ...