Find the average of two adjacent midpoints; for example:
(29.5 + 39.5)/2 = 34.5
34.5 is the class boundary between the two classes whose midpoints are 29.5 and 39.5.
Drop and raise that value a half-point for the class limits:
34.5 - .5 = 34
34.5 + .5 = 35
Thus we have , so far:
Midpoint.....Class Limits
29.5........... ___ - 34
39.5 .......... 35 - ___
Work with more adjacent pairs of midpoints to fill in the rest of the class limits.
The midpoints or class marks for the ages of the factory workers are 19.5, 29.5, 39.5, 49.5, 59.5 and 69.5. What are the class limits of this distribution??
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