Information about Mean standard deviation

Published on February 27, 2014

Author: ManishJaiswal12

Source: slideshare.net

No, of. Students 3 5 7 8 9 2.Calculate mean deviation from median from the following: Class Boundary Frequency 2-4 3 4-6 4 6-8 2 8-10 1 3.Find mean and standard deviation of ‘n’ natural numbers. 4. The mean and standard deviation of a group of 100 observations were found to be 20 and 3 respectively. After the calculations were made it was found that three of the observations were incorrect which were recorded as 21, 21, and 18. Find the mean and s.d. if the incorrect observations are omitted. 5. Ā is the mean of A1, A2, and A3. If a1, a2, a3 are the deviations of A1,A2, A3 from Ā respectively, prove that a12 +a22 + a32 = A12 +A22 + A32 – 3Ā 2. 6. If d2= mean square deviation about x, σ =standard deviation, and x-x = a, then show that d2 = a2 + σ2. 7. Compute the s.d. of income from the following: Income (Rs.) No.of earners: Below 200 25 200-399 72 400-599 47 600-799 22 800-999 13 1000-1199 7 8.Out of 400 observations, 100 observations have the value one and the rest of the observations are zero. Find the mean and s.d. of 400 observations together. 9. The mean and the variance calculated from a group of 80 observations are 63.2 and 25.93 respectively. If 60 of these observations have mean 64.8 and s.d. 4, find the mean and the s.d. of the remaining 20 observations. 10. The mean life in days and standard deviation for two types of electric bulbs are given below: Mean life in days Standard deviation in days Type I 310 9 Type II 260 14

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