The individual value plot illustrates the following properties of your data:

·    Dispersion. Each dot represents the difference between one or more pairs of observations.

·    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.

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

The individual value plot of the heart-rate data illustrates that most of the differences are positive and range from about -3 to +9. The graph also illustrates that m D is likely to be greater than the reference value specified by H0, since this value (0) is smaller than those within the confidence interval. Thus, it seems that the heart rates before treatment were significantly higher than the heart rates after treatment.