{"id":3578,"date":"2021-07-29T11:27:33","date_gmt":"2021-07-29T11:27:33","guid":{"rendered":"https:\/\/mathemerize.com\/?p=3578"},"modified":"2021-11-29T18:40:56","modified_gmt":"2021-11-29T13:10:56","slug":"measures-of-dispersion-statistics","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/measures-of-dispersion-statistics\/","title":{"rendered":"What are Measures of Dispersion Statistics ?"},"content":{"rendered":"
Here, you will learn what are the measures of dispersion in statistics i.e. range, mean deviation, variance and standard deviation with example.<\/p>\n
Let’s begin –<\/p>\n
The dispersion of a statistical distribution is the measure of deviation of its values about the their average(central) value.<\/p>\n
It gives an idea of scatteredness of the different values from the average value.<\/p>\n
Generally these measures of dispersion are commonly used.<\/p>\n
\n(i) Range <\/p>\n
(ii) Mean deviation <\/p>\n
(iii) Variance and standard deviation<\/p>\n<\/blockquote>\n
Range :<\/strong><\/p>\n
The difference between the greatest and least values of variate of a distribution, are called range of that distribution.<\/p>\n
If distribution is the grouped distribution, then its range is the difference between upper limit of maximum class and lower limit of a minimum class.<\/p>\n
\nAlso, coefficient of range = \\({difference of extreme values}\\over {sum of extreme values}\\)<\/p>\n<\/blockquote>\n
Mean deviation(M.D.) :<\/strong><\/p>\n
The mean deviation of a distribution is, the mean of absolute value of deviations of variate from their statistical average(Mean, Median, Mode).<\/p>\n
If A is any statistical average of a distribution that mean deviation about A is defined as<\/p>\n
\nMean deviation = \\({\\sum_{i=1}^{n}{|x_i – A|}}\\over n\\) (For ungrouped distribution)<\/p>\n
Mean deviation = \\({\\sum_{i=1}^{n}{f_i|x_i – A|}}\\over N\\) (For frequency distribution)<\/p>\n<\/blockquote>\n
NOTE : <\/strong>Mean deviation is minimum when it taken about the median.<\/p>\n\n\n
Example : <\/span>Find the mean deviation of the numbers 3, 4, 5, 6, 7.<\/p>\n
Solution : <\/span>We have n = 5, \\(\\bar{x}\\) = 5 here.
\n \\(\\therefore\\) Mean deviation = \\({\\sum_{i=1}^{n}{|x_i – A|}}\\over n\\)
\n = \\(1\\over 5\\)[|3 – 5| + |4 – 5| + |5 – 5| + |6 – 5| + |7 – 5|]
\n = \\(1\\over 5\\)[2 + 1 + 0 + 1 + 2] = 1.2
<\/p>\n\n\nVariance and Standard Deviation :<\/strong><\/p>\n
It is defined as the mean of squares of the deviation of variate from their mean. It is denoted by \\(\\sigma^2\\) or var(x).<\/p>\n
The positive square root of variance are called the standard deviation. It is denoted by \\(\\sigma\\) or S.D.<\/p>\n
\nHence standard deviation = + \\(\\sqrt{variance}\\)<\/p>\n<\/blockquote>\n
Hope you learnt what are measures of dispersion in statistics, learn more concepts of statistics and practice more questions to get ahead in the competition. Good luck!<\/p>\n\n\n