Lesson 1.4 – Displaying Quantitative Data: Stemplots

  • Make stem plots of quantitative data.
  • Interpret stemplots.
  • Compare distributions of quantitative data with stemplots. 

 

Activity: How many pairs of shoes do you own?

Photo Sep 15, 10 52 24 AMQuiz students on the three pairs of shoes pictured in the Activity.  #1: Reebok Pumps, #2: Toms, #3: Air Jordans.  Have students estimate how many pairs of shoes they own.  Students very easily entered the data into the SPA applet and created a stemplot.  Be sure that students are recording a key onto the paper.  Note: the key that is generated in the SPA applet is different for every student and may not even be one of the values in the data set.  No big deal.  The key is simply to show how the notation works.

 

Application 1.4 How many shoes are too many shoes?

Students used the applet to help them create a stemplot.  The biggest discussion was about describing shape when you have a back to back stemplot.  Easy for the distribution on the right, but it is backwards for the distribution on the left of a back to back stemplot.  Turn your head to the left and if the distribution looks skewed left, it is actually skewed right.  Have students think about where most of the values fall.  Do we have most values that are large with fewer and fewer as we get smaller (skewed left) or is it that most values are small with fewer and fewer as we get larger (skewed right).

 

Notes

Make the connection that the 3rd learning target from Lesson 1.4 is essentially the same as the 3rd learning target in Lesson 1.3 (hint: it will be the same in Lessons 1.5 and 1.8 as well….just with different types of displays).

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