The efficacy of an established screening test for detecting lung cancer in men and women between the ages 50 and 80 years is being evaluated at two different medical centers. Data from the study are collected during a span of 5 years. The results of the screening test disclose the following sensitivities and specificities

Center 1 Center 2

Sensitivity 75 65

Specificity 90 80

Which of the following is the most likely explanation for the difference in sensitivity between the two medical centers?

1. The incidence of disease is different between the two centers
2. The negative predictive value is different between the two centers
3. The positive predictive value is different between the two centers
4. The screening test was administered differently at the two centers