i) Since the data all fall within horizontal parallel lines, this plot only contains common causes. ii) The data exhibits seasonality. It would be useful to try to discover the cause of this seasonality. iii) The last point in the graph is a special cause because it is the highest point in the plot. It would be a good idea to find out what is different at the time this value occurred compared to the other times. iv) The last point in the graph is a special cause because it is much higher than any other values for the month of June. It would be a good idea to find out what is different about that June compared to the other months of June in the time frame. v) Both ii) and iii) are correct. vi) Both ii) and iv) are correct