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# Categorical data example

Video transcript

Lucio wants to test whether
playing violent video games makes people more violent. He asks his friends whether
they play violent video games and whether they have been
in a fight in the last month. He recorded the results
in the table shown below. Fill in the table to show
the fraction of each group of students who have
been in a fight. Then decide whether
there is an association between violent video games
and getting in a fight amongst Lucio's friends. So let's see what
they're doing here. So students who
play video games-- fractions who have been in a
fight, fraction who haven't. Students who don't play
violent video games-- fraction who have been in a
fight, fraction who haven't. So let's answer the
first part of this. Students who play
violent video games. So let's look at those students. So the students who play
violent video games-- it looks like Ellen plays
violent video games. Actually, let me just focus on
the data that we care about. So Ellen. So let's look at all the people
who play violent video games. So let's see. This column is
violent video games. So we have a yes here. So actually, we have both
of these right over here. And then we have down here. And then that's all of them. There's 1, 2, 3, 4, 5 people
who play violent video games. Now what fraction of them
have been in a fight? Well, it looks like 1 out of
the 5 have been in a fight. The rest of them have
not been in a fight. So we could say 1/5--
let's just write that down. So 1/5 have been in a fight. Fraction who haven't-- 4/5. So that's all these other nos. They play violent
video games, but they haven't been in a fight. 1, 2, 3, 4-- 4/5. So students who don't
play violent video games. Well, that's everyone else. And let's see how many
data points that is. That is 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15. So there's a total
of 15 students. And how many of them
have been in a fight? So let's see. We have 1. And then let's see,
1, and 2, and 3. So 3 out of the 15
have been in a fight. So 3 out of 15 is the
same thing as 1 out of 5. Those are equivalent fractions. And then the
fraction who haven't? Well, that's just going
to be everyone else. That's going to be 12
out of 15 or 4 out of 5. So based on Lucio's data-- and
this wasn't a huge sample size, obviously. He only found 5 kids who were
playing violent video games. And 1 of them had
gotten into a fight. So this isn't a
super rigorous study. But at least based
on his data, if we're trying to decide whether
there's an association between violent games
and getting into a fight amongst Lucio's friends, it
doesn't seem like there is. It seems like relatively,
whether or not they play violent video
games or not, 1/5 of them have been in a fight
in the last month. So it really doesn't
seem any difference. If this number was, I
don't know, 4/5, or 5/5, or all of them, then I'd say,
hey, even with Lucio's fairly small sample, I
would say, hey, maybe there is some type of
a strong association between playing violent
video games and fighting. But here you really
don't see any difference.