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Observe the following statements : (A)...

Observe the following statements :
(A) : 10 is the mean of a set of 7 obervations and 5 is the mean of a set of 3 observations. The mean of a combined set is 9.
(R ) : If `bar(x)_(i)(i = 1,2,…,k)` are the means of k - series `n_(i)(I = 1,2,3,…,k)` respectively, then the combined or composite mean is
`bar(x) = (n_(1)bar(x)_(1) + n_(2) bar(x)_(2) + ...+ n_(k)bar(x_(k)))/(n_(1)+n_(2)+...+n_(k))`

A

both A, R are true and `R rArr A`

B

both A, R are true and `R cancelrArr A`

C

A is true, R is false

D

A is false, R is true

Text Solution

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The correct Answer is:
D
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AAKASH SERIES-MEASURES OF DISPERSION (STATISTICS)-Practice Exercise
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  3. The mean deviation from mean of the data 90,100,125,115,110 is

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  4. The standard deviation of 7 scores 1,2,3,4,5,6,7 is

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  5. The standard deviation of 15 items is 6 and each item is decreased by ...

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  6. The standard deviation for the set of the numbers 1,4,5,7,8 is 2.45. I...

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  7. Standard deviation of 5,8,11,9,11 is

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  8. If the standard deviation of x(1),x(2),….,x(n) is 3.5 then the standar...

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  9. If the standard deviation of 0,1,2,3,4,5,6,7,8,9 is K, then the standa...

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  10. The variance of first 20 - natural numbers is

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  11. The variance of 6,8,10,12,14,16,18,20,22,24 is

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  12. Observe the following statements : (A) : 10 is the mean of a set of ...

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  13. A man motors from A to B. A large part of the distace is uphill and he...

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  14. An aeroplane files around a square, the sides of which measure 100 mil...

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  15. The mean of a data set consisting of 20 observation is 40. If one obse...

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  16. Mean of 100 observations is 50 and S.D. is 10. If 5 subtracted from ea...

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  17. Consider the following statements : (i) Mean of 100 observations is ...

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  18. I. The geometric mean of 2,4,16 and 32 is a II. The strength of 7 co...

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  19. If the mean deviation of number 1,1+d,…1+100d from their mean is 255, ...

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  20. The mean of 5 observations is 5 and their variance is 124. If three of...

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