MSM 709

Quantitative displays

Data set: Exam scores

40 81 83 86 75 78 78 91

64 50 68 64 72 70 95 82

82 83 82 86 59 75 55 98

Working with lists:

• Enter the data from the class in L1 by pressing STAT EDIT. Type in a number and use ENTER or the down arrow to proceed to the next entry.
• If there is already data in L1, place the cursor on the list name L1, hit CLEAR, then arrow down back into the list. This will erase the data.
• When you are done entering the data, simply use 2^nd QUIT to exit the spreadsheet. The list is automatically saved.

Activity 1: Histograms

Problem: Construct a histogram for the exam scores above.

a. Press 2^nd STATPLOT. Highlight Plot 1, then select On and choose the histogram. Enter the list containing the data you want to plot. (2^nd L1)

b. Press GRAPH. Do you see your histogram?

c. Press ZOOM and arrow down and select 9:ZoomStat.

d. Press TRACE to see the frequency of each class and also the class boundaries.

We can adjust the window manually and control the class boundaries or widths as follows.

a. Range = Max - Min; adjust Window so that the full histogram will display. For this example, set Xmin = 39.5 and Xmax = 99.5

b. Decide on class width. Generally, choose number of classes (square root of number of data points is one way to decide.) Then width = (Max -Min)/ # of classes. Set Xscl equal to the class width. Note: (Max - Min) / Xscl must be less than 47 on the TI-83. (i.e. must have fewer than 47 classes) For this problem choose the class width to be 10 and set the Xscl = 10.

c. Press GRAPH.

d. Describe the shape of the histogram. Relate the values of the descriptive statistics above to the shape of the distribution of data.

Activity 2: Stem-and-leaf plots; dotplots

Problem: Represent the change data in stem-and-leaf and in a dotplot.

The TI83Plus does not produce these graphs directly, but the can be done by hand easily if the data is in order.

1. Press STAT and choose 2:SortA. This command will sort the data in a specified list in ascending order. Likewise, 3:SortD arranges it in descending order. Enter the list that your data is in.

2. Press STAT and choose 1:Edit to look at your list.

3. Create a stem-and-leaf and a dot plot by hand.