Dear Student,
If we convert the above given series from cummulative to normal class intervals, then we will get,
 Class Interval Frequency Cummulative Frequence 161-162 2 2 162-163 6 8 163-164 11 19 164-165 13 32 165-166 13 45 166-167 13 58 167-168 27 85 168-169 8 93 169-170 7 100

Range is difference between the lower limit of the minimum interval and upper limit of the maximum interval of the grouped data
Range= 170-161
=9
Coefficent of range
$=\frac{Highest-lowest}{Highest+lowest}\phantom{\rule{0ex}{0ex}}=\frac{170-161}{170+161}\phantom{\rule{0ex}{0ex}}=\frac{9}{331}$
=0.027 or 0.03

Regards

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