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पाँच प्रेक्षणों के माध्य तथा प्रसरण क्रमश: 4.4 व 8.24 है यदि उनमें से तीन प्रेक्षण 1,2 व 6 हो, तो शेष दो प्रेक्षणों के मान ज्ञात कीजिए |

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माना शेष दो प्रेक्षणों के मान a व b है |
प्रश्नानुसार, `" माध्य "=4.4 =(1+2+6+a+b)/(5)`
`rArr" "a+b+9=22" प्रसरण =(मानक विचलन)"^(2)`
`rArr" "a+b=13" ....(i)"`
तथा `" प्रसरण "=(8.24)=(1)/(5)(1^(2)+2^(2)+6^(2)+a^(2)+b^(2))-(4.4)^(2)" (सूत्र "sigma^(2)=(1)/(n)Sigma x_(i)^(2)-M^(2)" का प्रयोग करने पर)"`
`rArr" "41.2=41+a^(2)+b^(2)-96.8`
`rArr" "a^(2)+b^(2)=97`
हम जानते है कि
`(a+b)^(2)+(a-b)^(2)=2(a^(2)+b^(2))`
`rArr" "169+(a-b)^(2)=2xx97`
`rArr" "a-b= pm 5`
समीकरण (i) व (ii) का हल करने पर `" ....(ii)"`
a=9, b=4 या a=4, b=9`
अतः शेष दो प्रेक्षण 4 व 9 है |

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