51 Risk factor for lumbar disease. One of the most common musculoskeletal disorders is lumbar disk disease (LDD).

Medical researchers reported finding a common genetic risk factor for LDD ( Journal of the American Medical Association , Apr. 11, 2001). The study included 171 Finnish patients diagnosed with LDD (the patient group) and 321 without LDD (the control group). Of the 171 LDD patients, 21 were discovered to have the genetic trait. Of the 321 people in the control group, 15 had the genetic trait.

a. Consider the two categorical variables group and presence/

absence of genetic trait. Form a 2 * 2 contingency table for these variables.

b. Conduct a test to determine whether the genetic trait occurs at a higher rate in LDD patients than in the controls. Use a = .01.

c. Construct a bar graph that will visually support your conclusion in part b .