Measures of Center and Variability

Seven students took a test. Each student has one score. Seventy-two. Eighty-five. Ninety. Ninety-two. Ninety-five. One hundred. The mean. Find the average of these scores.

Add all the scores, then divide by seven. The average is about eighty-eight. This is the average on the chart. The median. What is the middle score? The middle one. It is ninety.

The mode. Which score appears most often? This one, twice. Eighty-five. From the lowest to the highest. From seventy-two to one hundred, twenty-eight.

Six students skipped rope. Each has a number of jumps per minute. Forty-five. Fifty-two. Forty-eight. Fifty-five. Fifty. Forty-four. The mean. Find the average of these scores.

Add all the jumps, then divide by six. The average is about forty-nine. This is the average on the chart. What is the range of the jumps? From forty-four to fifty-five, eleven.

Seven numbers. Sort them and find the middle one. Three. Five. The median. What is the middle score? The middle one. The middle one is five. Now eight numbers. Sort them and find the middle. Three.

Five. Two numbers are in the middle. What is their average? The middle one. The median is five. Set 1. Find the mode and the range. Four. Six. Seven. Nine. The mode. Which value appears most often?

This one. This is the mode. What is the range? This is the range. Set 2. Find the mode and the range. Twelve. Fifteen. Eighteen. Twenty. The mode. Which value appears most often? This one.

This is the mode. What is the range? This is the range. Set 3. Find the mode and the range. Twenty-three. Twenty-five. Twenty-eight. Thirty. The mode. Which value appears most often? This one.

This is the mode. What is the range? This is the range. Ten students. Their weekly pocket money in yuan. Twenty. Twenty-five. Thirty. One hundred. The mean. Find the average of these scores.

Add all the money, then divide by ten. The average is about thirty-one point five. This is the average on the chart. The median. What is the middle score? The middle one. The median is twenty-five.

The mode. Which score appears most often? This one. Twenty appears four times. The one hundred pulls the average up. The median and the mode stay in the middle, so they represent most students better.

Class A. Ten students took the test. Seventy-five. Seventy-eight. Eighty. Eighty-two. Eighty-five. Eighty-eight. Ninety. Ninety-two. Ninety-five. The mean. Find the average of these scores.

Add all the scores, then divide by ten. The average of Class A is eighty-five. This is the average on the chart. What is the range for Class A? Class A range is twenty.

Class B. Ten students took the test. Sixty. Sixty-five. Seventy. Seventy-five. Eighty-five. Ninety. Ninety-five. Ninety-eight. One hundred. The mean. Find the average of these scores.

Add all the scores, then divide by ten. The average of Class B is about eighty-two point three. This is the average on the chart. What is the range for Class B? Class B range is forty.

Class A has a smaller range, so Class A is more consistent.