So sometimes, we're interested in not so 
much the, the, you know, the size of each
of these categories, but rather their 
relative sizes.
and so we're going to talk about relative 
frequencies and then try to, try to
create a pie chart. 
So first thing we're going to do is talk
about relative Freq...relative....uh, 
frequencies.
and so this would be computing the 
percentage of all cars that fit into each
of these categories And so the first 
thing we need to do is add up our total
frequencies. 
So, let's see, if I pull out my
calculator and add these up, I get 216 as 
the total number of reports that were
read. 
And so the relative frequency is, what is
the percentage. 
So 25 out of 216.
So that'd be 25 divided by 216 comes out 
to be about .1157, or about 11., let's
just say 11.6%. 
so that means, 11.6% of all of these
reports (no period) Were blue cars. 
we could do the same thing here for green
cars. 
52 out of 216 is about 0.24 07, or about
hm, 24.1%. 
And we could find the relative
frequencies for all of these colors, so 
I'm going to do that real quick.
And there's all of our relative 
frequencies.
So the idea of a pie chart now is that 
we're going to create a graph where we
have a circle that we're going to divide 
up into pie slices.
and so the idea is that the size of a pie 
slice should corresponid to the relative
percentage.so for example if I saw a 
slice like this.
that looks like it's about a quarter of 
the circle, so that should be about 25%.
Now, if you're getting really technical 
here and want to very precisely create a
pie chart, you can take each of these 
percentages and multiply it times 360
degrees. 
Well, of course you would need to convert
the percentage into a decimal first. 
And if you do that, you would come up
with a number of, it's about 38 degrees. 
And then you could use a protractor to
come up with the graph. 
But the reality is that most of the time
people don't bother doing that anymore 
because you know, we usually use
computers nowadays to create pie charts. 
But just for the fun of it, let's see if
we can free hand one pretty close. 
So, I'm going to start with green here
because 24% is awfully close to 25% so I 
would expect that to be just slightly
less than a quarter circle. 
So that's my green which is you know 24%,
well 24.1%. 
Okay, so let's maybe go to red now,
because red is going to be 19% and so 
that's going to be even less than 25%
right? 
let's see here if I divide this into five
pieces, each one would be another 5%.So 
it needs to be about 1/5 less than that
okay so maybe like That. 
Let's call that red.
And that's about 19%. 
and then white.
is going to be 18%. 
So that's going to be even a little bit
less than that one. 
That's pretty good.
I know that's not white. 
But white won't show up now very well,
would it? 
Uh,[LAUGH] and so we've got about 16.7%
there. 
and black is going to be similar, a
little bigger than white, a little less 
than red.
So maybe right around there. 
So we'll call that black.
And that one's 18.1 percent. 
And now we have blue and gray left, both
of which are going to be. 
lets see here.
Gray is going to be about half of that 
one.
So, eh, let's go with that. 
So there's blue, 11.6 percent, and then
we've got gray here with, 10.6 percent. 
Now this is a pretty lousy bar graph, pie
chart. 
Like I said, we'd be a lot lot better off
using a computer. 
But at least you get the idea of how we
form a pie chart by hand. 
The idea is that we want the relative
proportions, percentages of the circle to 
correspond with the relative frequencies
of our data.
