"\\begin{array}{c:c:c}\n \\begin{matrix}\n Class \\\\\n Interval\\\\ CI\n\\end{matrix}& \\begin{matrix}\n Frequency \\\\\n f\n\\end{matrix} &\\begin{matrix}\n Cumulative \\\\\n Frequency\n\\end{matrix} \\\\ \\hline\n 10-20 & 2 & 2 \\\\\n \\hdashline\n 20-30 & 8 & 10\n\\\\\n \\hdashline\n 30-40 & 6 & 16\\\\\n \\hdashline\n 40-50 & f_4 & 16+f_4\\\\\n \\hdashline\n 50-60 & 15 & 31+f_4\\\\\n \\hdashline\n 60-70 & 10 & 41+f_4\n\\end{array}"
"Estimated\\ Median=L+{{n \\over 2}-B \\over G}\\times w"
where:
"L" is the lower class boundary of the group containing the median
"n" is the total number of values
"B" is the cumulative frequency of the groups before the median group
"G" is the frequency of the median group
"w" is the group width
We have that "n=2+8+6+f_4+15+10=41+f_4"
"Median=50" The median lies in class interval "CI=50-60"
"L=50, n=41+f_4, B=16+f_4,G=15,w=10"
"50=50+{{41+f_4 \\over 2}-(16+f_4) \\over 15}\\times 10""{41+f_4 \\over 2}-(16+f_4) =0"
"41+f_4=32+2f_4"
"f_4=9" The missing frequency is "9."
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