ii) Mean deviation The mean deviation is the …：二）平均偏差值的平均偏差为…

ii) Mean deviation The mean deviation is the …：二）平均偏差值的平均偏差为… CLASS XI Subject- mathematics TOPIC:- MEASURES OF DISPERSION Teacher oriented Statistics is derived from Latin word status which means a political state. This suggests that statistics is an old as human civilization. The scope of statistics includes collection of numerical data purloining to almost every field, calculation of percentage, exports and imports, birth and deaths, marriage and divorces etc. It is useful in business, economics, sociology, biology, psychology, education, physics, chemistry, agriculture and related fields. The method of finding a representative value for the given data. This value is called the measure of central tendency Mean, Median and Mode are three measures of central tendency. A Measure of central tendency gives us a rough idea where data points are centered. But in order to make better interpretation from the data we should also have an idea how the data are scattered or how much they bunched around a measures of central tendency. Student oriented Students are well conversant with the methods of collection of a data, grouped data and graphical representation of data. The terms frequency distribution, discrete and continuous distributions, class interval, class maxe and range. Students have an idea about measures of central tendency like Mean, Median and Mode. Concept details The various measures of the central value i.e. Mean, Median and Mode give us a single value which represents the whole data. But these measures cannot adequately describe a set of observations, so it is necessary to describe some variation of the observations. The various measures of dispersion are:- i) Range. ii) Mean deviation and standard deviations. iii) Quantity deviation. i) Range: It is the difference between the minimum and maximum observations of data ii) Mean deviation: The mean deviation is the observations from the mean or median or mode of the data. Mean deviation for ungrouped data M.D. =1⁄ n ? ,xi -A, Therefore, M.D. ，x (bar)，=1⁄n ?,xi-A, where x(bar)=mean And M.D (M) =1/n ?,xi-M, where M=median Mean deviation for grouped data M.D. =1/N ?fi ,xi-A, where ?fi=N Thus, M.D. (x (bar)) =1/N ?fi , xi -x (bar), where x (bar) =Mean And M.D. (M) =1/N ?fi , xi -M, where M=Median The number M.D. (about mean) is called the coefficient of mean deviation (about Mean) Mean And the number M.D (about median) is called the mean deviation (about Median) Median Activity Diagnosis (Instant diagnosis) Diagnosis (Formative diagnosis) Levelwise Assisment 1) Find the range of the data: 35, 50, 48, 69, 39, 43, 72, 56, and 68. 2) Find the mean of first n natural number. 3) If the S.D. of the item x1, x2, x3,…….xn is ,. Write the S.D. of the item an1, an2, an3, …….ann. 4) Find mean deviation about median: 12, 5, 14, 6, 11, 13, 17, 8, and 10. 5) Find Mean deviation about median:- Class 0-10 10-20 20-30 30-40 40-50 50-60 Frequency 6 8 11 5 5 2