Classes
Class 9Class 10First YearSecond Year
$(xviii) The spread or scatterness of observations in a data set is called(a) average(b) dispersion(c) central tendency$

$(xxii) The positive square root of mean of the squared deviations of X_{i}(i=12 \ldots \ldots n) observations from their arithmetic mean is called(a) harmonic mean(b) range(c) standard deviation$

$(xv) The most frequent occurring observation in a data set is called(a) mode(b) median(c) harmonic mean$

$1. What do you understand by measures of central tendency?$

Example 2: Find the Range for the following distribution.\begin{tabular}{|c|c|}\hline Classes / Groups & \boldsymbol{f} \\\hline 10-19 & 10 \\\hline 20-29 & 7 \\\hline 30-39 & 9 \\\hline 40-49 & 6 \\\hline 50-59 & 7 \\\hline 60-69 & 1 \\\hline Total & 40 \\\hline\end{tabular}

$(vi) Arithmetic mean is a measure that determines a value of the variable under study by dividing the sum of all values of the variable by their(a) number(b) group(c) denominator$

$Example 2: A variable X takes the following values 45862 . Find the mean of X . Also find the mean when (a) 5 is added to each observation (b) 10 is multiplied with each observation (c) Prove sum of the deviation from mean is zero.$