In an infamous study, researchers suggested that left-handed individuals died younger than right-handed individuals. In the study, researchers identified 987 individuals who died in 1990 and then used historical records to determine birth year as well as whether the individual was righthanded or not. They found that individuals who were right-handed lived 75 years, on average, while those who were not right-handed (left-handed or ambidextrous) lived 66 years, on average. Explain the flaw in this retrospective study and point out the potential dangers in retrospective studies. Hint: In the early 1900s individuals were often pressured to become right-handed at an early age. This pressure subsided, and the percentage of individuals born around 1950 or later that are left-handed is around 10%–12%, the norm.