Stem-and-Leaf Plots Lesson 2-7 Part 2

What is a stem-and-leaf plot? A T-chart that is used to show numeric data and the distribution of numbers

Why would I want to use one? It displays a lot of numbers in a neater, cleaner, and organized way. It makes it easier to see how spread out the numbers are It is easier to identify outliers

Reading a Stem-and-Leaf Plot

Things you need to know… Stems –The stems include the digits in the tens place and higher –The top of the stem includes the first digits of the smallest number –The bottom of the stem includes the first digits of the largest number –Your stems need to include ALL consecutive numbers in between—even if there is no data for it.

Things you need to know… leaves –The leaves are all digits from ONLY the ones place –The leaves need to be organized from least to greatest –You can have multiples of the same digit per line

What does it look like? The stem-and-leaf plot below shows the number of students enrolled in a dance class in the past 12 years. The number of students are 81, 84, 85, 86, 93, 94, 97, 100, 102, 103, 110, and | 4 means 84

Should I skip numbers in my stem? This chart shows the number of infant deaths per 1,000 live births, of countries in Western Africa. No! You HAVE TO include all of the consecutive numbers from the first stem until the last one. Notice how 6, 7, and 10 have no data next to them. It means that no countries reported sixties, seventies, or one hundreds of infant deaths. You CANNOT put a zero in the leaf spot because that implies that you have data for that stem—which you don’t.

Making a Stem-and-Leaf Plot

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves

Finding the Range, Mode, Median, and Mean

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves Range= biggest number – smallest number 40 is the smallest number is the largest number 100 – 40 = 60 The range for this data set is 60 points.

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves Finding the Median (the middle number) Start counting with this leaf! Leaf number 12… This is the halfway point! I have 23 leaves. If I divided that in half, I would end up with This means that the 12 th number is my median ÷ 2 =  the 12 th number will be our median. The twelfth number is 73. This is my median.

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves Finding the Mode (the number that shows up most) You have more 7s than 9s or 0s. That means 67 is your mode. For the mode, look at each row of leaves separately. If you see more than one of a number, underline it. After looking at all your rows, pick the underlined number that has the most digits. 00

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves Finding the Mean (the average) To find the mean, you will be doing a combination of Multiplying, adding, and dividing.

This stem-and-leaf plot shows points that students received on a science quiz. StemLeaves Finding the Mean (the average) We will start by adding a zero to the end of the stem and then multiplying that number times the number of leaves you have.

StemLeaves Finding the Mean (the average) x 3 =120 50x 3 =150 60x 5 =300 70x 4 =280 80x 4 =320 90x 2 = x 2 =

StemLeaves Finding the Mean (the average) x 3 =120 50x 3 =150 60x 5 =300 70x 4 =280 80x 4 =320 90x 2 = x 2 = Now add up all your leaves. Look around the entire Stem-and- Leaf Plot. Try to make tens or multiples of five. This will make it easier for you to add quickly.

40x 3 =120 50x 3 =150 60x 5 =300 70x 4 =280 80x 4 =320 90x 2 =180 0x 2 = StemLeaves Finding the Mean (the average) X X X X X X X X X X XX 20 X X X 25 X

5015 StemLeaves Finding the Mean (the average) We have 23 leaves. Divide your sum by 23. ÷ 23 = Mean: Approximately 72.48