The boxplot illustrates the following properties of your data:

·    Shape. A boxplot can tell you a lot about the distribution of your data. The box represents the middle 50% of the differences. The line through the box represents the median difference. The lines extending from the box represent the upper and lower 25% of the differences (excluding outliers). Outliers are represented by asterisks (*).

·    Mean. The point below the plot labeled represents the mean difference between paired observations, which serves as your estimate of m D.

·    Confidence Interval. The line and brackets on either side of the mean represent the confidence interval. (See topic Confidence intervals below for more information.)

·    Reference Value. The point labeled H0 represents the value for m D specified in the null hypothesis.

The boxplot of the heart rate data indicates that the median difference is very close to the mean (2.333). Both the median and mean are substantially greater than the reference value specified in H0 (0). In fact, H0 is located very close to the left edge of the box. Therefore, we know that approximately 75% of the sample differences are greater than 0. Thus, it seems unlikely that m D is 0.

The 95% confidence interval for the mean difference also indicates that m D is greater than 0. Since H0 lies outside of the confidence interval, we can say with 95% confidence that m is not equal to 0, but is instead between 0.477 and 4.190.