Coach Z, the mid-distance running coach for the Olympic team of an eastern European country, claims that his six-month training program significantly reduces the average time to complete a 1500-meter run. Five mid-distance runners were randomly selected. Their times (in minutes) for the 1500-meter run were recorded before and after six months of training under Coach Z. The results are given below.
At an alpha level of .05, can we conclude that there has been a significant decrease in the meantime?

Question

Coach Z, the mid-distance running coach for the Olympic team of an eastern European country, claims that his six-month training program significantly reduces the average time to complete a 1500-meter run. Five mid-distance runners were randomly selected. Their times (in minutes) for the 1500-meter run were recorded before and after six months of training under Coach Z. The results are given below.
  At an alpha level of .05, can we conclude that there has been a significant decrease in the meantime?

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The Answer of Coach Z, the mid-distance running coach for the Olympic team of an eastern European country, claims that his six-month training program significantly reduces the average time to complete a 1500-meter run. Five mid-distance runners were randomly selected. Their times (in minutes) for the 1500-meter run were recorded before and after six months of training under Coach Z. The results are given below.
  At an alpha level of .05, can we conclude that there has been a significant decrease in the meantime?

Coach Z, the Mid-Distance Running Coach for the Olympic Team