Q30Long answer
- 40 4 40 - 50 5 50 - 60 3 STATISTICS 275 Solution Let A, the assumed mean, be 25.5. Here h = 10 xi – 25.5 Classes xi yi = fi fi y i f i yi2 1 - 10 5.5 –2 11 –22 44 10 - 20 15.5 –1 29 –29 29 20 - 30 25.5 0 18 0 0 30 - 40 35.5 1 4 4 4 40 - 50 45.5 2 5 10 20 50 - 60 55.5 3 3 9 27 70 –28 124 ∑ fi yi = −28 = − 0.4 x′ = ∑ fi 70 Mean = x = 25.5 + (–10) (0.4) = 21.5 h 2 Variance 2 (σ ) = N∑ fi yi2 − (∑ f y ) N 10 × 10 = [70(124) – (–28)2] 70 × 70 70 (124) 28 × 28 1240 = − = − 16 = 161 7×7 7×7 7 S.D. (σ) = 161 = 12.7