What are different methods of measuring dispersion. Sample of polythene bags from two manufactures, A, B, are tested by a prospective buyer for bursting pressure and the results are as follows.

Bursting Pressure		5-10	10-15	15-20	20-25	25-30	30-35
Number of bags manufactured by	A	2	9	29	54	11	5
	B	9	11	18	32	27	13

Which set of bags has more uniform pressure? If price are the same, Which manufacture’s bags would be preferred by buyer? Use appropriate statistical tool