The class size of a distribution is 25 and the first class-interval is 200-224. There are seven class-intervals:
(i) Write the class-intervals.
(ii) Write the class-marks of each interval.
Given, Class size = 25
First class interval = 200-224
(i) Seven class intervals are: 200-240, 225-249, 250-274, 275-299, 300-324, 325-349, 350-374
(ii) Class marks of 200-224: 
= 
= 212
Class marks of 225-249 = 
= 
= 237
Class marks of 250-274 = 
= 
= 262
Class marks of 275-299 = 
= 
= 287
Class marks of 300-324 = 
= 
= 312
Class marks of 325-349 = 
= 
= 337
Class marks of 350-374 = 
= 
= 362
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