Operation Crossroads was a 1946 military exercise in which atomic bombs were detonated over empty target ships in the Pacific 0cean.The Navy assigned sailors to wash down the test ships immediately after the atomic blasts. Thc National Academy of Science reported "that the overall death rate among operation-crossroads sailors was 4.6% higher than among a comparable group of sailors.. . . However, this increase was not statistically significant." (Tampa Tribune, Oct. 30,1996.)

a. Describe the parameter of interest in the National Academy of Science study.

b. Interpret the statement: "This increase was not statistically significant."