Credentialing and job practice in environmental health: an empirical study

To investigate the validity of the credentialing examination for entry-level practitioners in environmental health, 15 work measures, simulating or assessing important components of job practice, were developed. These work measures, along with the written examination, were administered to a sample of 128 entry-level practitioners drawn from 10 test sites throughout the country. Composite work measures were constructed in which individual work measures were weighted according to their judged importance. The total composite work measure, based on all 15 individual measures, correlated .53 with the total written examination. Correlations between composite work measures and the written test scores were generally in the .3 to .5 range and significant at the .01 level. Seventy-three percent of the sample were consistently classified on both the written examination and the total work measure composite. That is, 73 percent of the sample passed both the examination and the work measures or failed both the examination and the work measures. In comparison to similar studies, the magnitude of the coefficients reported here is acceptable to high. Results show that the examination is a valid, but not perfect, predictor of on-the-job skill in environmental health, and it should help to screen the public from the results of incompetent practice.