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