# Sample of polythene bags from a manufacturer are tested by a buyer for bursting pressure with the following data :

 Bursting Pressure (in lbs) : 5-9 9-13 13-17 17-21 21-25 25-29 29-33 No. of bags : 2 4 9 12 6 4 3

Calculate : (i) the standard deviation and (ii) the coefficient of variation.

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