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Graphing data on line plots

Sal shows measurements on line plots (also called dot plots).

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Video transcript

- [Voiceover] Let's get a little practice doing the Khan Academy exercise Marking Data on Line Plots. So right over here it says, "Tessa measured the distance "from her house to several locations "to the nearest half kilometer." All right, and so they have different locations and it tells us the distance from her house to each of these locations. So from her house to the school is 3 1/2 kilometers, from the library is 5 1/2 kilometers, to the park is two kilometers, the movie theater is four kilometers, to the post office, 5 1/2 kilometers. Then they ask us, "How many dots "should be on a line plot of these measurements?" So a line plot, and they have one down here, a line plot, this is literally a number line and what we do is we put as many dots there are at a certain point in the line. So if we have two data points at 5 1/2 we would put two dots right over there, but we'll get to that in a second. They're just asking us how many dots should be on the line plot of these measurements? Well, we should make a dot for each of these data points and there are one, two, three, four, five data points here. So there's five data points that I'm going to want to put on my line plot. Then they say, "Create a line plot "that shows all of the measurements. "Click above the marking on the number line "that matches each measurement. "Click higher to add more dots above the same marking. "Click lower to add fewer dots." So they say that the distance from the school to Tessa's house is 3 1/2 kilometers so we would want to put a dot at 3 1/2 and I do that just by clicking, clicking right over there, 3 1/2. So that's one data point at 3 1/2. Half way between three and four. Let's do it for the next ones. 5 1/2, that's the distance from the library to her house. 5 1/2, then we have two kilometers. Two kilometers, distance from ... Two kilometers was the distance from the park to her house. Then the movie theater if four kilometers. I wish you could see it all in one screen. Four kilometers. And then the post office is also 5 1/2 kilometers. So you actually have two data points at 5 1/2 kilometers. So right here I've just constructed a line plot. At different points on the number line I'm showing how many data points we have. So we have one data point at two kilometers, one at 3 1/2 kilometers, one at four kilometers, and two at 5 1/2 kilometers. Now notice, we said we would have five dots when we have one, two, three, four, five. One for each data point. Let's do this one more time. Let's check and make sure we got it right. Now let's do one more. All right, measure the length ... Measure the length of each line to the nearest quarter inch to collect data for the line plot below. To make your measurements, drag the ruler on top of the lines. Align the left end of the ruler with the left end of the lines then read the length of each line from the right end of the line. All right, so really I just wanna measure ... I just wanna measure, oh this is ... I didn't mean to tilt it like that. I just wanna measure each of these lines. So this green line right over here looks like it is six and this is split into one, two, three, four. It looks like it's 6 3/4ths. 6 3/4ths, the green line is 6 3/4ths inches long. So we have one data point at 6 3/4ths. So I'll put that right over there. Then we have the red line is ... Let's see, this is 7 2/4ths or 7 1/2. It's halfway between seven and eight. So 7 2/4ths or 7 1/2, so halfway between seven and eight is right over there. Then finally I have the purple line. The purple line, let's see. That is 8 3/4ths inches long. Notice I aligned it right at the beginning right over there and it goes all the way to eight and one, two, three out of the four. 8 3/4ths inches long, so let me, 8 3/4ths. So there you go. I have one line that was 6 3/4ths, one line that was 7 2/4ths or 7 1/2 and then one line that's 8 3/4ths inches long. Let's check our answer. Let's do one more. This is actually a lot of fun. All right, we gotta measure things again. So let's see, the green line. Green line is exactly three inches long, three inches long so let's plot it right over there. Then we have the red line is exactly, let's see, 3 3/4ths inches long. 3 3/4ths, let's put a dot right over there. Then the purple line is three inches long as well. So I have another data point at three inches. So two of the lines were three inches and one of them is 3 3/4ths and we are ... And we're done.