Q10 of 55 Page 364

If and let us find the value of


Let us write the modal class from the above frequency distribution table.

Given that, …(i)

∑fiui = 20


∑fi = 100


From the step deviation method, we have the relation of deviation (ui) and assumed mean (A).



Comparing it with equation (i),


A = 25


h = 10


Using the formula of step deviation method, we have



⇒


⇒ Mean = 25 + 2


⇒ Mean = 27


To find modal class, we need to find frequencies of the data given.



Note the greatest frequency in the data.


So, greatest frequency = 30


Thus, the corresponding class is 30 – 40.


⇒ Modal class = 30 – 40


Thus, mean is 27 and modal class is 30 – 40.


More from this chapter

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9

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i. Mean, median, mode are measures of ________.


ii. If mean of x1,x2,x3……..xn is mean of ax1,ax2,ax3……..axn is _________.


iii. At the time of finding arithmetic mean, the lengths of all classes are _______.

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Short answer type question :


Let us find the difference between upper class limit in median class and lower class limit of modal class of the above frequency distribution table.

 10

The following frequency distribution shows the time taken to complete 100 metre hardle race of 150 athletics :


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