Question: Are they right? Scientists say left-handers die sooner (SOURCE – The Detroit News, 1991) Southpaws face more than share of woe living in a world that is biased to the right. Now there’s a new worry: Scientists say they have found that left-handers die nine years sooner on average than right-handers. Researchers examined randomly selected death records of 987 people in Southern California. The researchers said right-handers, about 94% of the group, died at an average age of The left-handers died at an average age of 66. The researchers found that left-handers were six times more likely to die from an accident and four times more likely to die while driving a vehicle.

(Note that other research has failed to substantiate these claims.)

a. Was this an observational study or an experiment? Justify your answer.

b. Suppose that there may have been a disproportionate number of men – who are known die earlier than women on average – in the left-handers group. In this case, gender would be an example of __ _____.