Page 169 - DCOM203_DMGT204_QUANTITATIVE_TECHNIQUES_I

Quantitative Techniques – I

Notes 19. Find out standard deviation from the following data:
: 30 35 40 45 50 55 60 65 70 75 80
: 1 2 4 7 9 13 17 12 7 6 3
20. The mean of 150 observations is 35 and their standard deviation is 4. Find sum and sum of
squares of all the observations.
21. The mean and standard deviation of two distributions having 100 and 150 observations
are 50, 5 and 40, 6 respectively. Find the mean and standard deviation of all the 250
observations taken together.
22. The mean and standard deviation of 100 items are found to be 40 and 10. If, at the time of
calculations, two items were wrongly taken as 30 and 70 instead of 3 and 27, find the
correct mean and standard deviation.
23. The sum and the sum of squares of a set of observations are 75 and 435 respectively. Find
the number of observations if their standard deviation is 2.
24. The sum and the sum of squares of 50 observations from the value 20 are -10 and 452
respectively. Find standard deviation and coefficient of variation.
25. The mean and standard deviation of marks obtained by 40 students of a class in statistics
are 55 and 8 respectively. If there are only 5 girls in the class and their respective marks are
40, 55, 63, 75 and 87, find mean and standard deviation of the marks obtained by boys.
26. There are 60 male and 40 female workers in a factory. The standard deviations of their
wages (per hour) were calculated as 8 and 11 respectively. The mean wages of the two
groups were found to be equal. Compute the combined standard deviation of the wages of
all the workers.
Answers: Self Assessment

1. representative 2. same,different
3. dispersion 4. averages of first order
5. averages of second order 6. True
7. False 8. True

9. True 10. True
11. rigidly 12. based on
13. extreme observations 14. fluctuations
15. False 16. True

17. True 18. True
19. range 20. largest and smallest
21. coefficient of range 22. False
23. False 24. False

25. (c) 26. (b)
27. (b) 28. (b)
29. False 30. False
31. True 32. True

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