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Question
Which measure of dispersion is the best and how?
Solution
Standard Deviation is the best measure of dispersion as it satisfies the most essentials of the good measure of dispersion. The following points make Standard Deviation the best measure of dispersion:
- Most of the statistical theory is based on Standard Deviation. It helps to make a comparison between the variability of two or more sets of data. Also, Standard Deviation helps in testing the significance of random samples and in regression and correlation analysis.
- It is based on the values of all the observations. In other words, Standard Deviation makes use of every item in a particular distribution.
- Standard Deviation has a precise value and is a well-defined and definite measure of dispersion. That is, it is rigidly defined.
- It is independent of the origin.
- It is a widely used measure of dispersion as all data distribution is nearer to the normal distribution.
- It enables algebraic treatment. It has correct mathematical processes in comparison to the range, quartile deviation, and means deviation.
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RELATED QUESTIONS
A measure of dispersion is a good supplement to the central value in understanding a frequency distribution. Comment.
Some measures of dispersion depend upon the spread of values whereas some are estimated on the basis of the variation of values from a central value. Do you agree?
If in the previous question, each worker is given a hike of 10 % in wages, how are the mean and standard deviation values affected?
The average daily wage of 50 workers of a factory was Rs 200 with a standard deviation of Rs 40. Each worker is given a raise of Rs 20. What are the new average daily wage and standard deviation? Have the wages become more or less uniform?
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Range
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Compare the values of different measures for each crop.
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Q.D.
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Mean deviation about Mean
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Mean deviation about Median
The yield of wheat and rice per acre for 10 districts of a state is as under:
|
District |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| Wheat |
12 |
10 |
15 |
19 |
21 |
16 |
18 |
9 |
25 |
10 |
| Rice |
22 |
29 |
12 |
23 |
18 |
15 |
12 |
34 |
18 |
12 |
Calculate for each crop,
Standard deviation
Calculate the mean deviation using mean and Standard Deviation for the following distribution.
|
Classes |
Frequencies |
|
20 - 40 |
3 |
|
40 - 80 |
6 |
|
80 - 100 |
20 |
|
100 - 120 |
12 |
|
120 - 140 |
9 |
|
|
50 |
