CT scanning for lung cancer. A new type of screening for lung cancer, computed tomography (CT), has been developed.

Medical researchers believe that CT scans are more sensitive than regular X-rays in pinpointing small tumors.

The H. Lee Moffitt Cancer Center at the University of South Florida conducted a clinical trial of 50,000 smokers nationwide to compare the effectiveness of CT scans with X-rays for detecting lung cancer. (Todays’ Tomorrows, Fall 2002.) Each participating smoker was randomly assigned to one of two screening methods, CT or chest X-ray, and his or her progress tracked over time. The age at which the scanning method first detects a tumor is the variable of interest.

a. Identify the data collection method used by the cancer researchers.

b. Identify the experimental units of the study.

c. Identify the type (quantitative or qualitative) of the variable measured.

d. Identify the population and sample.

e. What is the inference that will ultimately be drawn from the clinical trial?