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## Making and describing scatterplots

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# Example of direction in scatterplots

AP Stats: DAT‑1 (EU), DAT‑1.A (LO), DAT‑1.A.2 (EK), DAT‑1.A.3 (EK), DAT‑1.A.4 (EK) CCSS Math: 8.SP.A.1

## Video transcript

The graphs below
show the test grades of the students
in Dexter's class. The first graph shows the
relationship between test grades and the amount of time
the students spent studying. So this is study
time on this axis and this is the test
grade on this axis. And the second graph
shows the relationship between test grades
and shoes size. So shoe size on this
axis and then test grade. Choose the best description
of the relationship between the graphs. So first, before looking
at the explanations, let's look at the actual graphs. So this one on the
left right over here, it looks like there is a
positive linear relationship right over here. I could almost fit a line
that would go just like that. And it makes sense
that there would be, that the more time
that you spend studying, the better score
that you would get. Now for a certain
amount of time studying, some people might do
better than others, but it does seem like
there's this relationship. Here it doesn't
seem like there's really much of a relationship. You see the shoe sizes,
for a given shoe size, some people do not so well
and some people do very well. Someone with a size 10
and 1/2, it looks like, someone it looks like
they flunked the exam. Someone else, looks like
they got A minus or a B plus on the exam. And it really would be hard
to somehow fit a line here. No matter how you draw
a line, these dots don't seem to form a trend. So let's see which of
these choices apply. There's a negative
linear relationship between study time and score. No, that's not true. It looks like there's a
positive linear relationship. The more you study, the
better your score would be. A negative linear relationship
would trend downwards like that. There is a non-linear
relationship between study time and score and a negative
linear relationship between shoe size and score. Well that doesn't
seem right either. A non-linear
relationship, it would not be easy to fit a line to it. And this one seems like a
line would be very reasonable. And it doesn't seem like
there's any type of relationship between shoe size and score. So I wouldn't pick
this one either. There's a positive
linear relationship between study time and score. That's right. And no relationship between
shoe size and score. Well, I'm going to
go with that one. Both graphs show
positive linear trends of approximately equal strength. No, not at all. This one doesn't show
a linear relationship of really any strength.

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