Stem and Leaf and Scatter Plots
Date: 10/13/98 at 23:01:44 From: Kyle Curre Subject: Scatter plots and stem and leaf plot graphs Hi. I am desperately trying to find out what stem and leaf and scatter plots are. I have searched everywhere for an explanation of what they are and how to make them. I am doing a math project for Pre-Algebra, and I have to use stem and leaf and scatter plots. My teacher wants us to be resourceful and find out all the information we need ourself. Thanks again, Kyle Curre
Date: 10/14/98 at 09:20:13 From: Doctor Statman Subject: Re: Scatter plots and stem and leaf plot graphs Dear Kyle, A stemplot is a graphical display that is used to represent one column of data. A scatterplot represents the relation between two columns. Here are two examples. Suppose I had one column of data that contained the following numbers: 10 11 15 26 28 28 29 31 31 32 37 38 Look at the number 10, and think about it as a stem (1) plus a leaf (0). So 10 becomes 1 | 0, writing the stem, then a bar, then the leaf. Look at the 11. The 11 becomes 1 | 1, with the same stem as the 10. So you can think of the 10 and the 11 as two leaves on the same stem like this: 1 | 01 Now I'll put the rest of the stems and leaves for these numbers together: 1 | 015 2 | 6889 3 | 11278 Can you see the stems for the 10's, 20's, and 30's? Can you see how many 28's are in the data? Do you see how to break the numbers up into stems and leaves? Pretty cool, right? Now a scatterplot is different - you need two columns of data. Here are the heights and weights of the people in my family: Height Weight (inches) (pounds) Dad 73 185 Mom 65 125 Kid 1 50 55 Kid 2 43 45 Kid 3 38 33 Kid 4 27 24 I can plot these two columns against each other in a scatterplot. I made this one in a computer package called Minitab. Scatterplot - - 180+ + Dad - Weight - - - 120+ + Mom - - - - 60+ + - + - + - + - --------+---------+---------+---------+---------+-------- Height 30 40 50 60 70 Do you see how there are six people in my family and six points (+) on the scatterplot? Each plus sign is one person - I find their height on the horizontal or x axis, and then I find their weight on the vertical or y axis, and I put a + sign where they meet. If you need more help, I suggest you visit a site like this one by Rex Boggs called Exploring Data, from Queensland, Australia: http://exploringdata.cqu.edu.au/ It has some good stuff about stemplots and scatterplots. I hope this helps. Good luck with your project. Statistically yours, - Doctor Statman, The Math Forum http://mathforum.org/dr.math/
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