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Hello my name is Beth Dixon and this is part two of the video series on frequency distribution and histograms
this series has a set of goals given raw data construct a frequency distribution relative
frequency distribution percent frequency distribution and histogram
given frequency distribution find the lower class limits upper class limits and the class width and three and four which I won't read
to keep the video short we are dividing these videos - this PowerPoint into a series of videos in the first
video we covered frequency distribution in this video we will cover the relative frequency distribution and percent frequency distribution
so next we will start
by finding the relative distribution and the percent distribution for each class
but first let's do a quick review of our percents
and to do this let's do it in context
of looking at a sample of fruit
we have three apples
three bananas
for a total of six fruit
we want to look at the number of apples compared to the total number and we want to compare the two numbers by division
so we have three apples over the total of six which gives us 3/6
and that reduces to ½
and if we change that to a decimal
gives us
0.50 or
50% and remember that to change a
decimal to a percent
Weems simply move the decimal places
two places to the ride so it would move from here
to here
now for some terminology
that of course is your fraction
it has always been your fraction it still is your fraction but notice we use the reduced form of the fraction
the decimal number is called the relative number
because it tells us
and relates the number of apples to that total number of fruits that's the new terminology
and of course has always the last number is the percent it is the percent of
fruit that is an apple
back to where we left our table if you watched video one you helped create this table or created it as you watched that if not just assume that
we have a table here and this is where we're starting
from video one you will remember that our frequency
, adds up to 40 or our total number of data was 40 students
and this is the weight of those students
and we want to find the relatively excuse me not the relatively but the relative frequency
and the relative frequency gives the relative number in each class in other words it
compares by division the number or frequency in the class to that total number
and expresses that number as a decimal
its most
it's much easier to show than to say especially since I seem to be tongue tied today as I am recording this
the relative frequency of the first class
is bailed by taking that frequency three
and dividing it by 40 which gives us the decimal
0.075
you to simply take three divided by 40 in your calculator to do this and that relative number or the relative frequency
change back to my arrow here
is going to be
0.075
and we will proceed to do the second class the same way will take their relative excuse me the frequency five
divide by 40
that will give this 5/40
and gives is zero
0.125
and proceed to figure it out for the third class
which would be nine divided by 40 which is going to give us 0.225
12 divided by 40 gives us 0.30
and we added the zero here
for use in just a second
five divided by 40 which gives is 0.125
four divided by 40 which gives us 0.10 again I'm adding the extra zero at the end for use in just a minute
and then two divide about 40 which gives is 0.05
now that we've got the relative frequency
of the last number here that does complete a relative frequency column
and we can find and proceed to find the percent frequency which gives the percentage in each class
this is where we express the percent of numbers in each class and to find this we will simply
change the relative frequency into a percent by moving our decimal
over two places to the right
adding the percent sign
we will take the decimal from here moving two places to the right and move our decimal here
that will change that number to 7 1/2% -- 7.5%
we move our decimal from here
to there and that will give us
12.5%
moving our decimal from here
to in between the two and five
gives us 22.5% and here's why we added the zero because we need to move two places
if you hadn't added the zero before you can stop and do that right now
so we're going to move it two places to the right and that becomes 30%
two places to the right again becomes 12.5%
here's the other place where we added the zero so we would have two places 10% and we add two places here the last entry becomes 5%
and that completes our
percent frequency table
and that concludes the video --- this part of the video in this part the video series in the next
section will pick up where we left off here and work on a histogram
thank you for watching and please continue watching
All spelling errors are mine...please no laughing or comments. Beth Dixon