Stem-and-Leaf Plots - Free Educational videos for Students in K-12

Stem-and-Leaf Plots - By Anywhere Math

Transcript


00:0-1	Uh huh . Welcome anywhere . Math . I'm Jeff
00:01	Jacobson . And today we're gonna learn one way to
00:04	organize your data a little more visually . And that
00:07	is to use a stem and leaf plot . Let's
00:10	get started . Okay . Example one make a stem
00:31	and leaf part of the length of 12 cell phone
00:33	calls . And that's length in minutes . Here's our
00:36	data over here . Uh to make the stem and
00:38	leaf plot . I'm gonna show you step by step
00:40	how to do it . And the first step ,
00:43	as always when we have data , first step is
00:45	to order or the data . Okay , I've got
00:51	my data in order . I'm just gonna double check
00:53	real quick to make sure . I didn't forget any
00:55	values . 123456789 10 11 12 . There were 12
01:01	cell phone calls . So I'm good . Uh Now
01:03	step to make the stem and leaf plot and to
01:06	do that . We start off with a cross .
01:09	Yeah . Okay . Something like that . On the
01:13	left top left , you're gonna write stem . That's
01:17	where the stem goes . So naturally on the right
01:19	is where the leaf is . Okay . Now from
01:23	here , you have to decide what your stem is
01:25	gonna be . And if I look at my data
01:27	, I go all the way from 2 to 55
01:30	with that kind of range . I'm going to go
01:33	by tens for my leaf . So first , well
01:37	2356 What do they have in the tense place ?
01:41	Well it's not there , but you can put a
01:43	zero there . Right ? So that's a zero in
01:46	the tense place . Then I go all the way
01:49	up . 1234 and five . Okay . 55 was
01:56	my last , my last value . That's the highest
01:58	value . There's a five in the 10th place .
02:00	So I can stop there . There's nothing , there
02:03	were no phone calls that were 60 minutes and something
02:06	uh notice I didn't skip any any numbers when you're
02:10	making your stem and leaf plot whatever you decide for
02:12	your stems , you cannot skip Any values . Okay
02:16	so I can't go 123 And then 456 even .
02:21	It doesn't matter if there's any values on that stem
02:25	. It doesn't matter . You can't skip anything .
02:27	You got to go directly in order until you're finished
02:30	wherever you need to stop at the end . Okay
02:32	so that's my stem . Yeah , This represents the
02:36	10th place here . The leaf is representing my one's
02:40	place . So look at your values . Well for
02:44	the values that have a zero in the 10th place
02:46	, I have a 235 and six . So we
02:50	put those in order here . 23 56 Okay .
02:56	Just like that next . Well what values have a
02:59	one in the 10th place ? Well I've got the
03:01	10 , 14 and the 18 . So now I'm
03:04	writing the ones value here for the leaf . So
03:07	I've got 04 and eight 048 . And we keep
03:13	doing that . Well I've got to 23 so that
03:16	would be 3330 . Is there's a 30 , so
03:22	I'm gonna put a zero there that represents 30 .
03:26	I also have a 36 . So I put a
03:28	six Notice there is no numbers in the 40s .
03:34	Okay . So do I put a zero there or
03:37	leave it blank ? Well , if you said leave
03:40	it blank , you're right . If I put a
03:42	zero there , that would mean a phone call of
03:46	40 minutes . Just like this zero here represented 30
03:50	minute phone call . But I don't have any phone
03:52	calls in the forties . So I leave it blank
03:55	. Go to the last 15 So I'm gonna put
03:58	a five there . So this is my stem and
04:01	leaf plot . We're almost done now . Step three
04:05	. Really really important not to forget . This is
04:09	to make a key . Okay . And the key
04:14	is really really important basically all you do is you
04:17	pick any example here for any value . I'm gonna
04:22	put the key over here . Hopefully you can see
04:25	that . Okay . Yeah so the key . Let's
04:28	say I'm gonna do this . Two . Yeah three
04:33	Like that . So a stem of two and a
04:35	leaf of three . That means 23 . Okay I
04:42	guess I should put minutes to I don't really have
04:44	room but 23 minutes . Okay so that's my key
04:48	. You can box and if you want or you
04:49	don't need to . But the whole point is give
04:52	an example from your data . Okay so that we
04:55	know exactly what the stem represents . Uh and the
04:59	leaf as well . Okay Good . Here's 1 to
05:02	shine your own . Okay . Example to we've got
05:12	three different questions notice we already have the stem and
05:15	leaf plot over here . Um So instead of making
05:18	it now , we're interpreting a stem and leaf plot
05:22	. So let's just look over this real quick .
05:24	Uh The data is about test scores and points .
05:27	How many points they got a test score notice are
05:30	key here . Uh nine for our stem and two
05:34	for our leaf means that represents a 92 for 92
05:38	points uh on the test . So let's look here
05:42	. First one . How many students scored ? Less
05:44	than 80 points ? Well , all of these here
05:48	are in the 80 point range less than that ?
05:51	Well , that would be a 78 77 75 70
05:56	66 . So we have 123455 students scored Less than
06:02	80 points . Next one B How many students scored
06:07	at least 90 points , At least . That means
06:10	90 points or greater . So let's see this zero
06:15	here . That's 90 . Exactly . So there's 123
06:19	and 11 person got 100 points . So that's four
06:23	, Four students got at least 90 points . And
06:28	the last one . How are the data distributed ?
06:30	So that just means uh what's kind of the shape
06:33	or how is it spread out ? Um So if
06:36	you notice we have kind of a few , just
06:39	kind of one student was pretty low , one student
06:42	was really high . Everybody else is kind of in
06:45	the middle , right ? So let's say that ,
06:48	how are the data distributed ? Yeah . Most students
06:56	, we're in the middle . Mhm . Mhm .
07:01	And we can say around , Yeah . Ah we
07:06	could stay around 80 , Probably the exact middle .
07:09	Maybe around 80 84 points . Mhm . Oops .
07:15	Oh Around 84 points . Okay . Now 11 last
07:20	thing you'll notice with the stem and leaf plot .
07:22	When I did the example before I put commas ,
07:25	you don't need to do that . I probably shouldn't
07:26	have done that . Uh notice here . All you
07:29	need to really do is just list the numbers for
07:31	the for the leaf so don't worry about doing commas
07:34	. And also if you're wondering , well can we
07:37	use this for decimals ? Like what if my data
07:40	is decimals and yes you can and what it's gonna
07:44	look like . Let's say you've got 6.79.2 and so
07:50	on . Well you can make it where this line
07:54	represents the decimal point . So I could do something
07:57	like 6789 here I put a seven there A two
08:05	here and then your key would be like people Right
08:09	, six that line seven equals 6.7 . Okay .
08:15	That's why the key is so important so that we
08:17	know exactly what is representing . Okay , here's one
08:22	more to try on your own . Thank you so
08:30	much for watching , and if you like this video
08:32	, please subscribe .

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