Q2 of 145 Page 370

If the mean of 25 observations is 27 and each observation is decreased by 7, what will be the new mean?

Mean of the observation is given by –


Total number of observations = 25


Mean of 25 observation = 27 (Given)


We get



⇒ Sum of 25 observations = 27 × 25 = 675


If each observation is decreased by 7, the Sum gets affected.


New Sum = 675 – (25 × 7) = 675 – 175 = 500



Thus, new mean = 20


More from this chapter

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1

If the mean of 5 observations x, x + 2, x + 4, x + 6 and x + 8 is 11, find the value of x.

 3

Compute the mean of the following data:

















Class



1 - 3



3 - 5



5 - 7



7 - 9



Frequency



12



22



27



19


 4

Find the mean, using direct method:





















Class



0 - 10



10 - 20



20 - 30



30 - 40



40 - 50



50 - 60



Frequency



7



5



6



12



8



2


 5

Calculate the mean of the following data, using direct method:



















Class



25 - 35



35 - 45



45 - 55



55 - 65



65 - 75



Frequency



6



10



8



12



4