In the accompanying figure, look at the curve of performance over trials, which is generally upward except for the dip at trial 2. Is the dip just a chance variation, or is it a reliable, nonchance drop?
By indicating the lower and upper confidence limits for each mean, a graph can convey at a glance the reliability that goes with each point. Calculate a 95 percent confidence interval for each mean. Pencil in the lower and upper limits for each point on the graph. Write a sentence explaining the dip at trial 2.
