Question

From the data given below find out mean
x f
20-40 2
40-60 7
60-80 9
80-100 24
100-120 9
120-140 7
140-160 2

Answer 1

Answer:

Mean 90

Step by step Explanation:

$\begin{tabular}{|l|l|l|l|}</p><p>\cline{1-4}</p><p>Class interval(x) & Frequency(f) & Class mark(xi) & x_if_i \\ \cline{1-4}</p><p>20-40 & 2 & 30 & 60 \\ \cline{1-4}</p><p>40-60 & 7 & 50 & 350 \\ \cline{1-4}</p><p>60-80 & 9 & 70 & 630 \\ \cline{1-4}</p><p>80-100 & 24 & 90 & 2160 \\ \cline{1-4}</p><p>100-120 & 9 & 110 & 990 \\ \cline{1-4}</p><p>120-140 & 7 & 130 & 910 \\ \cline{1-4}</p><p>140-160 & 2 & 150 & 300 \\ \cline{1-4}</p><p>Total & 60 & & 5400 \\ \cline{1-4}</p><p>\end{tabular}$

Direct Mean Method:

$Mean = \frac{sum \:of\: all \:observation}{Total \:observation}\\\\ \bar x=\frac{\Sigma x_i f_i}{\Sigma f_i}\\\\\\\bar x=\frac{5400}{60}\\\\\bar x= 90$

Hope it helps you.