Corrections
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Mohammed MA, Worthington P, Woodall WH. Plotting basic control charts: tutorial notes for healthcare practitioners *Qual Saf Health Care* 2008;**17**:137–45. An error has occurred in the appendix for this paper: In the row ‘Continuous data (*x*) of which there are *n* items’ and the column ‘Three-sigma control limits’, 2.26 should be 2.66.