Value based interpretation of pulmonary function tests.

Two contrasting errors in spirometric interpretation are the inappropriate conclusion of "normality" (type I) and of "abnormality" (type II). A survey of 67 health professionals showed major interpersonal and intersituational differences in opinion about the optimal relative proportions of type I and type II errors. This suggests the need for caution in the commonly employed practice of interpretation based on a 5 percent false positive rate.