Correlation between the yearly values of two solar parameters and the sunspot number. Left top: scatterplot between the MgII index and the sunspot number (colored asterisks), together with the corresponding best-fit lines (black). Left bottom: scatterplot between the yearly number of active regions and the sunspot number. Right top: difference between the MgII index and the correlated sunspot number normalized by the MgII index. Best-fit line (black) and lines with slopes that are two standard deviations above or below the best-fit line slope (two blue dashed lines) are also included. Right bottom: corresponding normalized difference between the yearly number of active regions and sunspots.