Cumulative meta-analysis of 9 trials of intravenous streptokinase for acute myocardial infarction showing the application of the prediction (equation 2) using the results of the first 5 trials. The cumulative z-statistic is plotted versus the cumulative number of participants, shown on a square root scale (see Appendix). The horizontal dashed line indicates the two-sided critical value of the z-statistic at α = 0.01. The diagonal dotted line emanates from the origin and passes through the point representing the meta-analysis of the first 5 trials (double circle). The location where this line intersects the horizontal dashed line is marked by a vertical dotted line projecting down to the horizontal axis and indicating the predicted number of participants required to obtain statistical significance.