It has been known that a fixed dose of a certain drug results to an average increase of pulse rate by at least 15 beats

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It has been known that a fixed dose of a certain drug results to an average increase of pulse rate by at least 15 beats per minute. A group of 25 patients given the same dose showed the following pulse rate in beats per minute: 15, 12, 10, 8, 14, 15, 16, 11, 7, 13, 9, 10, 12, 11, 9, 10, 17, 14, 15, 7,9, 18, 20, 13, 12. Is there a proof to show that this group will have a lower pulse rate (less than 15 beats/ min)? (use 0.05 level of significance)