mean

# A. Dot (line) plots (See Appendix C.)

# Sample Dot Plot:

x 1

x x

x 4

x x

x x x x x

x x x x

x x x

x x

2

3

5

6

7

8

9

# Once the dot plot is completed, you can answer the following questions:

iii. What seems to be the most common response?

i. ii

What is the shape of the distribution of the data? . What is the range of the data?

# B. Histograms

Let’s now introduce the use of the calculator for graphical data display. On your TI-84 go to STAT, 1:Edit, and enter all the data into L1. Arrow down after each data entry. Then go to Stat Plot (2nd y=). Enter Plot 1 and turn ON. Arrow down to Type:. Arrow right to histogram and press ENTER. For Xlist, enter the number of the list in which the data are stored – for example, (L1). Then press ZOOM 9 to see the histogram. Note the similarities and/or differences between the dot plot on the board and the histogram on the screen. Press TRACE to see the actual number of data entries in each column.

# Measures of Center

Now that you have the class data both listed in your calculator and on the board in the form of a dot plot, we are ready to think about what we mean by the “center” of the data. There are three common ways to measure the center, and the words all begin with the letter “m” – mean, mode and median.

# Mean

The mean is the arithmetic average. To find the mean, add up all the values in the data set and then divide by the number of data entries in the set. For example, if you wanted to find the average number of people living in a house for all the students in your class, you would add up the number of people living in each student’s house, then divide by the number of houses represented by the students in the class. The result would be the arithmetic mean (commonly called the average); that is, the

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