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70 UNIT 1 Exploring One-Variable Data

test to their classes and grade the test together. Mr. Starnes’s students earned an
average score that was 8 points higher than the average for Ms. McGrail’s class.
Ms. McGrail wonders whether Mr. Starnes might have “adjusted” the class
rosters from the computer scheduling program. In other words, she thinks he
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might have “stacked” his class. He denies this, of course.
To help resolve the dispute, Mr. Starnes provides data on the cumulative
grade point averages of the students in both classes from his computer. The
following table displays the data.

2.900 3.300 3.980 2.900 3.200 3.500 2.800 2.900 3.950
McGrail
3.100 2.850 2.900 3.245 3.000 3.000 2.800 2.900 3.200
2.900 2.860 2.600 3.600 3.200 2.700 3.100 3.085 3.750
Starnes
3.400 3.338 3.560 3.800 3.200 3.100

Based on these data, did Mr. Starnes stack his class? Give appropriate graph-
ical and numerical evidence to support your conclusion.

You can use technology to make boxplots, as the following Tech Corner illustrates.

3. Tech Corner MAKING BOXPLOTS

TI-Nspire and other technology instructions are on the book’s website at bfwpub.com/tps7e.

The TI-83/84 can plot up to three boxplots in the same viewing window. Let’s use the calculator to make
parallel boxplots of the overall rating data for Apple and Samsung tablets.

1. Enter the ratings for the Apple tablets in list L1 and those for the Samsung tablets in list L2.
2. Set up two statistics plots: Plot1 to show a boxplot of the Apple data NORMAL FLOAT AUTO REAL RADIAN MP
and Plot2 to show a boxplot of the Samsung data. The setup for
Plot1 is shown. When you define Plot2, be sure to change L1 to L2. Plot1 Plot2 Plot3
On Off
Note: The calculator offers two types of boxplots: one that shows Type:
outliers and one that doesn’t. We’ll always use the type that identifies Xlist:L1
Freq :1
outliers. Mark :
Color: BLUE

3. Press ZOOM and select ZoomStat to display the parallel boxplots. NORMAL FLOAT AUTO REAL RADIAN MP
Then press TRACE and use the arrow keys to view the five-number Plot1: L1
summary.

Med=84

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