1.2 Dot Plots and Stem and Leaf Plots.notebook
August 22, 2014
1.2 Displaying Quantitative Data
There are 3 ways to display numerical data.
1. dot plots
2. stem and leaf plots
3. histograms
What to look for in numerical graphs
1. center (mean or median)
2. spread (range or standard deviation)
3. shape (skewed left, skewed right, symmetric)
4. any unusual values
Sep 6­2:56 PM
Aug 22­2:55 PM
Ex.1
Gas Mileage for 2009 midsize cars
What to look for
1. center, shape, spread, possible outliers
2. Comparing words between the two groups
Aug 22­2:59 PM
Ex.2 Compare the household size for these two countries.
Aug 22­3:11 PM
A stem and leaf plot is good for small data sets.
• It separates each number in a data set into a stem (the beginning
digit or digits) and a leaf (the last digit or digits).
• There is a column of all stems and at each stem, the corresponding
leaf digit line up to the right.
ex. data: Ages of adults at the DMV
22, 26, 31, 36, 36, 38, 44, 46, 51
2
3
4
5
Aug 22­3:23 PM
2 6
1 6 6 8
4 6
1
key: 2 2 = 22 years old
Aug 23­12:07 PM
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1.2 Dot Plots and Stem and Leaf Plots.notebook
August 22, 2014
Sometimes, you want to split the stem into two or more parts.
• For example, use leaves 0-4 on the first line and 5-9 on the second line.
Ex.4 Comment on this back to back stem and leaf plot.
key 1|8 = 18 years old
Ex.3 Construct and summarize a stem and leaf plot for this data.
Sep 6­3:10 PM
Sep 6­3:25 PM
Assignment: p.42 #38, 44, 46, 50
Sep 6­3:36 PM
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