Each day, an electronics manufacturer creates thousands of small fan motors for computers. The speed (i.e., revolutions per minute) with which the motors run must be in a certain range. Motors that run too slowly will not cool a computer properly; motors that run too fast will wear out prematurely. The following R chart monitors the amount of variability of the speed (in rpm's) of subgroups of 7 motors that have been selected each hour for testing:

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