Which two of the following statements are true? a) The sum of the deviations from mean (ignoring algebraic signs) is greater than the sum of the deviations from median (ignoring algebraic signs) b) Standard deviation is independent of change of origin and change of scale c) In a symmetrical distribution, mean deviation equals 4/5 of standard deviation d) In a symmetrical and bell shaped distribution quartile deviation is 1/3 of standard deviation Choose the correct answer from the options given below
Which two of the following statements are true? a) The sum of the deviations from mean (ignoring algebraic signs) is greater than the sum of the deviations from median (ignoring algebraic signs) b) Standard deviation is independent of change of origin and change of scale c) In a symmetrical distribution, mean deviation equals 4/5 of standard deviation d) In a symmetrical and bell shaped distribution quartile deviation is 1/3 of standard deviation Choose the correct answer from the options given below Correct Answer a) and c)
Below are the explanation of the above statements:
1.Deviation:
- Method of Mean Deviation does not give accurate results.
- The reason is that the mean deviation gives the best results when deviations are taken from the median.
- But the median is not a satisfactory measure when the degree of variability in a series is very high.
- And if we compute mean deviation from mean that is also not desirable because the sum of the deviations from the mean (ignoring signs) is greater than the sum of the deviations from the median (ignoring signs).
- If the mean deviation is computed from a mode that is also not scientific because the value of mode cannot always be determined. Thus, statement A is correct.
2. Standard deviation is independent of the change of origin and but not of scale. Thus, statement B is incorrect.
3. In a symmetrical distribution, the mean deviation equals 4/5 of standard deviation. Thus, statement C is correct.
4 In symmetrical and bell-shaped distribution, quartile deviation is the distance from the median to the lower quartile or to the upper quartile. Thus, statement D is incorrect.