Course: AP®︎/College Statistics > Unit 2Lesson 2: Representing a quantitative variable with histograms and stem plots
A stem and leaf is a table used to display data. The 'stem' is on the left displays the first digit or digits. The 'leaf' is on the right and displays the last digit. For example, 543 and 548 can be displayed together on a stem and leaf as 54 | 3,8. Created by Sal Khan.
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- What are some applications of this? Never seen it used in real life? @0:00do baseball statisticians use this?(254 votes)
- I've seen it used on a Ferry timetable with the stem having the hours and the leaf having the minutes... Actually gave you a decent sense of the peak running times when there were extra services... at a glance. Then you could look closer and get the exact times.(214 votes)
- Why do you use Stem-and-Leaf Plots? You could just write the numbers the way Sal did when he was explaining it.(114 votes)
- In addition, Stem-and-leaf plots condense the data, so you won't have to list all the numbers. It's easier to find the mean, median, and range, even if the list of numbers is organized least to greatest.(7 votes)
- Can you make a stem and leaf plot using four digit numbers? Example-1,000(14 votes)
- Yes, but you need to have the leaves as single digits so the stems have to be appropriately numbered. For example, you might have values that range from 1105 to 1204. Your stems would have to be 110, 111, 112, 113... 120(10 votes)
- What is the need of stem and leaf plots in our life?(12 votes)
- it is useful if you want to become a statistician or a data-scientist.(5 votes)
- this is really hard i need a strategy to learn this? i need your help!(1 vote)
I suggest you try the practice session on Reading Stem and Leaf Graphs. http://www.khanacademy.org/math/arithmetic/interpreting-data-topic/reading_data/e/reading_stem_and_leaf_plots
When you get to a problem you can't figure out, just use the "I need a hint" button.
You will be an expert in Stem and Leaf graphs in no time.
Good luck!(23 votes)
- At2:13doesn't he say 9 instead of 7?(7 votes)
- I think Sal had made enough work hours to be allowed to make some mistakes from time to time...(4 votes)
- I’m confused. Can someone explain?(6 votes)
- In a stem and leaf plot the left number is equal to 10 times that number. The right number is equal to 1 times that number(6 votes)
- Where is Sal's key? Generally in a Stem and Leaf Plot, there is a key at the bottom.(6 votes)
- While no key is present in the video, Sal seems to have a key on a separate piece of paper/in his head, the key in particular being, for example, 5|6=56(3 votes)
- Who invented stem and leaf plots?(4 votes)
- Arthur Bowley in the early 20th Century:
- still do not get where leaf numbers come from(4 votes)
- The leaf number is not actually separate numbers. In a stem and leaf plot, the stem is like the first digit and the stem would be the number following it. For example, in number 24, the 2 is the stem and 4 would be the leaf. In the table, in sal's video, you read from left to right. you take the stem and tack the leaf number at the end. For example, the last number would be 20.(3 votes)
A statistician for a basketball team tracked the number of points that each of the 12 players on the team had in one game. And then made a stem-and-leaf plot to show the data. And sometimes it's called a stem-plot. How many points did the team score? And when you first look at this plot right over here, it seems a little hard to understand. Understand we have 0, 1, 2 under leaf you have all of these digits here. How does this relate to the number of points each student, or each player, actually scored? And the way to interpret a stem-and-leaf plot is the leafs contain-- at least the way that this statistician used it-- the leaf contains the smallest digit, or the ones digit, in the number of points that each player scored. And the stem contains the tens digits. And usually the leaf will contain the rightmost digit, or the ones digit, and then the stem will contain all of the other digits. And what's useful about this is it gives kind of a distribution of where the players were. You see that most of the players scored points that started with a 0. Then a few more scored points that started with a 1. And then only one score scored points to started with a 2, and it was actually 20 points. So I'm going to actually write down all of this data in a way that maybe you're a little bit more used to understanding it. So I'm going to write the 0's in purple. So there's, let's see, 1, 2, 3, 4, 5, 6, 7 players had 0 as the first digit. So 1, 2, 3, 4, 5, 6, 7. I wrote seven 0's. And then this player also had a 0 in his ones digit. This player, I'm going to try to do all the colors, this player also had a 0 in his ones digit. This player right here had a 2 in his ones digit, so he scored a total of 2 points. This player, let me do orange, this player had 4 for his ones digit. This player had 7 for his ones digit. Then this player had 7 for his ones digit. And then, let me see, I'm almost using all the colors, this player had 9 for his ones digit. So the way to read this is, you had one player with 0 points. 0, 2, 4, 7, 9 and 9. But you can see, and it's kind of silly saying the zero was a tens digit, you could have even put a blank there. But the 0 lets us know that they didn't score anything in the tens place. But these are the actual scores for those seven players. Now let's go to the next row in the stem-and-leaf plot. So over here, all of the digits start with, or all of the points start with 1, for each of the players. And there's four of them. So 1, 1, 1, and 1. And then we have this player over here, his ones digit, or her ones digit, is a 1. So this player, this represents 11. 1 in the tens place, 1 in the ones place. This player over here also got 11. 1 in the tens place, 1 in the ones place. This player, let me do orange, this player has 3 in the ones place. So he or she scored 13 points. 1 in the tens place, 3 in the ones place. 13 points. And then I will do this in purple. This player has 8 in their ones place. So he or she scored 18 points. 1 in the tens place, 8 in the ones place. 18 points. And then finally, you have this player that has the tens digit is a 2. And then the ones digit is a 0. I'll circle that in yellow. It is a 0. So he or she scored 20 points. So looking at the stem-and-leaf plot, we were able to extract out all of the number of points that all of the players scored. And once again, what was useful about this, is you see how many players scored between 0 and 9 points, including 9 points. How many scored between 10 and 19 points, and then how many scored 20 points or over. And you see the distribution right over here. But let's actually answer the question that they're asking us to answer. How many points did the team score? So here we just have to add up all of these numbers right over here. So we're going to add up, I'll start with the largest, so 20 plus 18 plus 13 plus 11 plus 11-- 13, 11, 11-- plus 9 plus 7 plus 7 again plus 4 plus 2. Did I do that right? We have two 11's, then a 9, then two 7's, then a 4 then a 2, and then these two characters didn't score anything. So let's add up all of these together. So 0 plus 8 is 8, plus 3 is 11, plus 1 is 12, plus 1 is 13, plus 9 is 22, plus 7 is 27, 34, 38, 40. So that gets us to 40. Let me do that one more time. 8, 11, 11, 12, 13, 22, 29, 29, and then 29, 36, 40, and 42. Looks like I actually might have messed-- let me do that one more time. This is the hardest part, adding these up. So let me try that one last time. I'm just going to state where my sum is. So 0, 8, add 3, 11, 12, 13, 22, 29, 36, 40, 42. So it's a good thing that I double checked that. I made a mistake the first time. 4 plus 2 is 6, 7, 8, 9, 10. So we get to 102 points. The team, in total, scored 102 points.