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 what is the difference between assumed mean method and step deviation method?

in which kind of sums do we use the 2 types of finding the mean of different data?

please explain as i am confused bout which method to use in which sum.

@ Apurva: Good attempt. Well done and Keep it up!

@ Aditya: Your friend has nicely explained both the methods. Step-deviation is used while we are handling with large values of fi and xi.

 

Hope it helps you!

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Both assumed mean method and step deviation method are ways to find mean without any complications...

step deviation method is just an elaboration of assumed mean

I will tell u both the methods......

1. Assumed Mean method:

Step 1- Tabulate the continuous class intervals and frequency alongwith class marks.

  Class Mark = Upper Limit + Lower Limit

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Step 2- Assume any of the class marks to be your  mean .

Step 3- Take out the differences of the assumed mean and class marks.{ xi - a = di}

Example if the class marks are 20, 30,40,50,60,70 and so on......and if the a =50 then,di is -30,-20,-10,0,10,20and so on.....

Step 4: Multiply fi and di .

Step5:  

  d  = sum of fidi

  sum of fi

Step 6:  Mean = a + d

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2.Step deviation method :

do the same as assumed Mean method till step 3

after that do as folows:

Step 4:  ui = di / h  { h = class size}

Step 5: multiply fi and ui .

Step 6: u (bar) = sum of fidi / sum of fi

Step 7: x (bar) = a + u (bar) h

If u use the first method and see that the calculations are complicated then use step deviation method to easily get the mean

if the calculations are easy then , continue with the Assumed mean method......!!!!!!!!!!!!!!!!!

That was quite easy , wasn' t it ????
Hope u understood it.!!!
If yes then , like it!!!
 
 
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