Mini Lesson 2: Showing and describing variability How do I make a dot plot (and scale an axis)? Data...
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Transcript of Mini Lesson 2: Showing and describing variability How do I make a dot plot (and scale an axis)? Data...
Mini Lesson 2: Showing and describing variability
How do I make a dot plot (and scale an axis)?
Data Literacy Project
Begin with a question:
How did students in my class do on the quiz?
The following data set represents the grades earned by 23 students on a 10 point quiz.
Grades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
Making a dot plot is a 2 step process:
1. Scale the axis2. Plot the dots
Note: For a dot plot, you will only need to scale one axis (usually the horizontal axis) for your data. The other axis will simply be a count or frequency of the number of times each value appears in the data set.
1. Scale the axisa. Find the lowest and highest scores in the data
set (the range).
Scores:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
What is the lowest score for the quiz data set? _____
What is the highest score for the quiz data set? _____
1. Scale the axisb. Put the highest and lowest grades on the axis so it
will include the full range of your data set.Grades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
- the X-axis does not have to start at zero - the Y-axis does not require a label (although “count”
or “frequency” would be appropriate)
1. Scale the axisc. Put tic marks at equal intervals along the
axis.Grades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
- The major tic marks are labeled and are at intervals of 1.0.- Note that not all of the quiz scores are whole numbers....
1. Scale the axisd. Set minor tic marks at equal intervals
between the major tic marksGrades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
- What value does each minor tic mark represent?
1. Scale the axisd. Set minor tic marks at equal intervals
between the major tic marksGrades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
ANSWER
5.5 6.5 7.5 8.5
- the minor tic marks do not need to be labeled
2. Plot the dotsPlot each case using a dot for each student’s grade.
Grades:9, 7.5, 8, 7, 9, 6, 8, 7, 9, 5, 8.5, 8, 5, 6.5, 8, 9, 6, 7, 8, 7, 5, 6.5, 7.5
- There are 3 dots over the grade of 5 because three students got a grade of 5 on the quiz. (5 appears three times in the data set).
What if one of the grades does not fall on a tic mark?
How would you plot a grade of 7.2?Indicate on the graph below where a grade of 7.2 would appear.
What if one of the grades does not fall on a tic mark?
How would you plot a grade of 7.2?Indicate on the graph below where a grade of 7.2 would appear.
ANSWER
How much do wild bears weigh?
Twelve wild bears were caught, anesthetized, and their bodies were measured and weighed.
The data are a sample of data supplied with MiniTab and are attributed to Dr. Gary Alt
Weight (pounds)
14218014212239614011682
18036879
160
Weight (pounds)
14218014212239614011682
18036879
160
ANSWERHow much do wild bears weigh?
The bears in this sample weigh from around 76 pounds to almost 400 pounds. Most of them weigh between 79 and 180 lbs. There were two very big bears.