Question

If assumed mean a=7, then for which class di=0?​

Answer 1

Answer:

Assumed mean is simply the change of origin. If an arbitrary constant 'a' is subtracted from each observation then that constant value 'a' is often referred as assumed mean. We take assumed mean just to simplify our calculation. Usually we take it while calculating arithmetic mean using short cut method. Moreover, there is no hard and fast rule and you can take any value from your observation as assumed mean, it will not change the final answer.

For Ex:

Suppose if the given observations are 0, 10, 20, 30, 30, 40, 50, 60, 70.

you can take any of the given observations as assumed mean, but if you take 30 as assumed mean you will get -30, -20, -10, 0, 0, 10, 20, 30, 40.

Now it would become easier for you to add these values and calculate their mean as half of the values will cancel out. After this you can simply add 30(assumed mean) to the mean to get the final answer.

So mostly middle observations or the observations which appear more often in a given set of data are taken as assumed mean as they simplify our calculation to the maximum.