LESSON 3 An Average Activity

Mrs. Dewey's class was collecting data on the heights of fourth-graders. She asked a doctor to talk to the class about how children grow and develop. One of the things Dr. Solinas talked about was the average height of ten-year-olds. What does “average” mean?

“It was just an average day.”

“The doctor said my height is above average for kids my age.”

“We really need rain. Rainfall this year has been well below average.”

“My average grade in spelling is 75 percent.”

“Our soccer team averages about three goals per game.”

Each sentence describes what is usual or typical for the situation.

Scientists and mathematicians use averages to help them describe data they have collected. Doctors who study how children grow measure the heights of many children. Then, they use this data to find the average height for different age groups. They use one number, an average, to represent the heights of a whole group.

The average value for any set of numbers, such as the average height of fourth-graders, can be calculated in more than one way. You have already learned about one kind of average—the mode. In this lesson you will learn about a second kind of average—the median. You can find the median of a set of numbers easily and use it to describe the data you collect. Later this year, you will learn to calculate a third kind of average.