BMJ 1994;308:339 (29 January)

Letters

Statistical analysis inappropriate

EDITOR, - S C Darby and colleagues' study of cancer and atmospheric nuclear weapons tests raises some interesting methodological questions.1 Exposed servicemen and civilians working with nuclear weapons were compared with a control group matched for age and occupation and with the general population by means of national mortality statistics. Two sided tests and 95% confidence intervals were used to compare the exposed group with the general population. One sided tests and 90% confidence intervals were used to compare the exposed group with the control group. The tests were done in the direction of the observed difference.

In a one sided test the alternative hypothesis is that there is a difference in a specified direction. The null hypothesis is then that there is no difference or a difference in the opposite direction. This is reasonable if a difference in the opposite direction would have the same meaning or result in . . . [Full text of this article]


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?

Access all current jobs at BMJ Group
Whats new online at Student BMJ
Listen to the latest BMJ Interview