2 The following 95% confi dence intervals represent the difference in the percentage with gingivitis in a comparison of male and female young adults. The null hypothesis is that the true percentages are equal for males and females. Suppose that a difference in percentages of 5% is of clinical importance. Match the inferences (i–v) with the options (a–e).

Options for male percentage minus female percentage (↔ denotes confi dence interval):

0 5 10 0 5 10 –5 0 5 10 0 5 10 –10 –5 0

(i) Evidence that a greater percentage of females have gingivitis (ii) Strong evidence that a greater percentage of males have gingivitis – all values within the confi dence interval are of clinical importance (iii) The P- value is slightly greater than 0.05 (iv) No differences within the confi dence interval are of clinical importance (v) The null hypothesis is plausible.