Justification for nswer

Submitted by Reeta on Sat, 02/25/2012 - 10:38

Hi.

    I am not able to understand the following questions pls how is the answer correct ?

 

The answer is :-
 
The correct answer is B.
 
You use the PERT calculation (P + 4M + O)/6 to compute a weighted average of the totals, which in this case equals $273,333. This number represents the mean (or 50 percent point). Therefore the probability of the project coming in at $273,333 is 50 percent. The probability of $270,000 (since it is less than the mean) is less than 50 percent. 
 
Source: PxMaPm( rP)r eEp
Page: 191
 
But how it is 50% can you explain me pls.
 
 

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redarrow (not verified)

Mon, 02/27/2012 - 12:45

It is 50% because:

if you will examine the formula; it could be restated as the summation of "n" divded by "N"; where n represents every single sample, and N represents the total population of the sample.

in that question, n = 3 (these are n1 = P; n2 = 4M and n3=O) where as N = 6; hence 3/6 = 50%