In a group of patients presenting to a hospital casualty department with abdominal pain, 30% of patients have acute appendicitis. Seventy per cent of patients with appendicitis have a temperature greater than 37.5°C, 40% of patients without appendicitis have a temperature greater than 37.5°C.

(a) The sensitivity of temperature greater than 37.5°C as a marker for appendicitis is 21/49.

(b) The specifi city of temperature greater than 37.5°C as a marker for appendicitis is 42/70.

(c) The positive predictive value of temperature greater than 37.5°C as a marker for appendicitis is 21/30.

(d) The predictive value of the test might be different in another population.

(e) The specifi city of the test will depend upon the prevalence of appendicitis in the population to which it is applied.