11-Unit11

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Unformatted text preview: = The co-efficient of mean deviation = = = 356.72 ΣfD/N 356.72/50 7.13 mean deviation / mode 7.16/ 18.3 .3912 Merits of Mean Deviation 1. Mean deviation is simple to understand and easy to calculate 2. It is based on each and every item of the distribution 3. It is less affected by the values of extreme items compared to standard deviation. 4. Since deviations are taken from a central value, comparison about formation of different distribution can be easily made. Sikkim Manipal University Page No. 197 Research Methodology Unit 11 Demerits of Mean Deviation 1. Algebraic signs are ignored while taking the deviations of the items. 2. Mean deviation gives the best result when it is calculated from median. But median is not a satisfactory measure when variability is very high. 3. Various methods give different results. 4. It is not capable of further mathematical treatment. 5. It is rarely used for sociological studies. Standard deviation Standard deviation is the most important measure of dispersion. It satisfies most of the properties of a good measure of dispersion. It was introduced by Karl Pearson in 1893. Standard deviation is defined as the mean of the squared deviations from the arithmetic mean. Standard deviation is denoted by the Greek letter  Mean deviation and standard deviation are calculated from deviation of each and every item. Standard deviation is different from mean deviation in two respects. First of all, algebraic signs are ignored in calculating mean deviation. Secondly, signs are taken into account in calculating standard deviation whereas, mean deviation can be found from mean, median or mode. Whereas, standard deviation is found only from mean. Standard deviation can be computed in two methods 1. Taking deviation from actual mean 2. Taking deviation from assumed mean. Formula for finding standard deviation is (x-x)2 / N Steps 1. Calculate the actual mean of the series x / N 2. Take deviation of the items from the mean ( x-x) 3. Find the square of the deviation from actua...
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This note was uploaded on 04/15/2010 for the course MBA mba taught by Professor Smu during the Spring '10 term at Manipal University.

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