In this video I want to show you how to make a relative frequency chart.
As you will see, this is very similar to a normal frequency chart and when we end up
scaling back the values using the total frequency.
Let me be a little bit more specific about what we will do.
So in a relative frequency chart, we definitely want to list out how often we see each of
our data values appear, then we will take our total frequency and divide, so we can
get a relative frequency.
When we are all done we will take the sum of all those relative frequencies and double-check
that they all add up to 1.
In a sense, it's like you are finding a percentage of how often something will appear.
Let's get some data and see what this looks like in practice.
Okay, so in my data I have the daily number of absences at some given school.
We can see that on day 1 there are 4 absences, day 2 had 3 absences, day 3, 0 absences, so
on and so forth.
So, you know, give me any day and I will tell you how many students missed on that day.
I am going to start off building my chart by just listing out all of my data values
then all of their frequencies, and then we will actually build the relative frequency.
So, absences, frequency, and we will leave some space for the relative frequency.
Alright, let's see what data values we have.
Looks like I have 0, 1, 2, 3, 4, and 5.
Alright, that looks pretty good so far.
And now I want to list how often each of these data values appear.
So I see I have a couple of 0s, 2, 1, 2, 3 ones; 1, 2, 3, 4 twos; 1, 2, 3 threes.
Just two 4s and only one 5.
So if this was just a normal frequency chart I'd stop right there but now we're going
to calculate the relative frequency for each of our absences.
Before we get there, I need a total amount of frequency, and this should be the same
number as the number of data points I have.
So I can say I have 15 days here, this should be 15.
To catch any mistakes that you may have made at this point, go ahead and run through and
add up these values to make sure that they do add up to 15.
If they don't you can double check to make sure that you have written the right number.
Alright, so I am at 15, I know I'm on the right track.
Alright, let's make some relative frequency.
We'll take each of these values and divide it by the total frequency, 2 divided by 15.
So I am getting .33 repeating, I'm going to round this to just .13.
On to the next one, 3 divided by 15.
So .20, .27, so I'm rounding this one up, .20, .13, and .07.
Alright, so you can see that in the relative frequency, what I was saying when I said this
is like a percentage.
Because if I wanted to know, well, how often can I expect to see, say, 3 absences in my
list, it will show up there about 20% of the time.
Let's go ahead and add our relative frequency to see if it adds up to 1.
Sure enough, the total is 1, so I know I am on the right track.
And that's how you make a relative frequency chart.
You just scale back all of your frequencies using the total frequency.