average number of people per household for students in your class. To find the mean response for your activity question above (What is the importance of mathematics in society?), take the sum of all of the responses and divide by the number of persons who responded. With so many data entries, that would take a long time, but your calculator will do it for you instantly. Here’s how:

With your data in List 1, go to STAT, arrow right to CALC, press 1 for 1-Var Stats. Now the cursor is asking where your data is, so enter L1 (2^{nd }1) and press ENTER. The symbol x-bar (“x” with a bar over it) represents the mean. What is the mean response for your data? (See Appendix C.)

## Practice problems:

1.

a) Mr. Sneed’s math class earned the following scores on their midterm exam: 81, 67, 93, 71, 65, 61, 32, 81, 83, 92, 81, 80. What is the mean score for Mr. Sneed’s class? (Enter the data for Mr. Sneed’s class into List 2) [73.9]

b)

Mrs. Short wanted to compare her class’s scores with Mr. Sneed’s scores. Her students got the following exam grades: 98, 65, 77, 73, 70, 81, 89, 84, 64, 68, 95, 56, 81. What was the mean score for Mrs. Short’s class? (Enter the data for Mrs. Short’s class into List 3) [77]

c)

Whose class did better? Are you sure? (See Appendix C.)

d)

What was the most common score in each of the classes? (Make histograms for the data in List 2 and in List 3 and compare the shapes of the two histograms.)

# Mode

That last question (#1d) leads us to the definition of another measure of center, the mode. The mode is the value that occurs most frequently in a set of data values. A data set may have one mode, or more than one mode, or no mode at all! What is the mode for Mr. Sneed’s exam scores? [81] Mrs. Short’s exam scores? [There is no mode] What is the mode for the set of observations your class collected in response to the “importance of math” question? How do you know? [The mode would correspond to the tallest column.]

# Median

One of the most useful measures of center is the median. The median is the middle value when all the data are arranged in numerical

47

mode

median