निम्नलिखित वर्गीकृत बारम्बारता बन्टन का समान्तर माध्य 54 है , तो p का मान ज्ञात करो
`{:("वर्ग अन्तराल : ",0-20,20-40,40-60,60-80,80-100),("बारम्बारता :" ," "7," "p, " "10," "9," "13 ):}`

Explanation

स्पष्ट है की
A = 50 , N = 39 + p , h = 20 , ` sum f_(i) u_(i) = 21 - p " तथा " overline(X) = 54`
`therefore overline(X) = A + h{(1)/(N) sumf_(i)u_(i)} `
`rArr 54 = 50 + 20 xx{(21-p)/(39 + p)}`
` rArr 4 = 20 xx{(21 -p)/(39 + p)}`
`rArr 1 = 5 ((21-p)/(39 + p)) rArr 39 + p = 105 - 5p rArr 6p = 66 rArr p = 11`