make frequency polygon

Score - 32-34 , 35-37 , 38-40 , 41-43 , 44-46 , 47-49 , 50-52 !

Frequency - 13 , 12 , 20 , 18 , 15 ,10 , 4 .

@Kshitj_Singham: Good answer! Keep posting!

 

The given frequency distribution is not continuos. So, firstly convert it into a continuos frequency distribution. The difference between the lower limit of a class and upper limit of the preceding class is i.e. h = 1. To convert the given frequency distribution into a contributions frequency distribution, subtract  from each lower limit and add  to each upper limit. The distribution so obtained is given below.

Score31.5 – 34.534.5 – 37.537.5 – 40.540.5 – 43.543.5 – 46.546.5 – 49.549.5 – 52.5
Frequency1312201815104

 

Histogram and frequency polygon of the obtained data:

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 First, we'll make this continous....

Lets consider any classes...say 32-34 & 35-37...

The lower limit of any of 35-37 = 35

The upper limit of 32-34 = 34

Difference = 35-34 = 1

Half the difference = 1/2 x 1 = 0.5

Therefore, new class interval of 32-34 :

(32-0.5)-(34+0.5) = 31.5 - 35.5

Like this, we'll do for all the class intervals...so we get :

Score - 31.5-34.5 , 34.5-37.5 , 37.5-40.5 , 40.5-43.5 , 43.5-46.5 , 46.5-49.5 , 49.5-52.5

Freq - 13, 12, 20, 18, 15, 10, 4

Now we'll take middle points or class mark of class intervals on X-axis and the frequency on Y-axis.

Class Mark of 31.5-34.5 = 31.5 + 34.5 / 2 = 33 and we'll calculate for all the class intervals....

Therefore, we'll get the following table :

Class Mark ( X axis) - 33, 34, 39, 42, 45, 48, 51

Freq (Y axis) - 13, 12, 20, 18, 15, 10, 4

Now, you have got the coordinates...now its easy to plot... :)  thumps up plzzz !!  :)

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Thumps up plz....

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