A study aimed to investigate difference in lifespan between left-handers and right-handers. To control for influences such as genetics, upbringing, and education, they studied pairs of twins in which one twin was left-handed and the other was right-handed. Out of 118 such pairs of twins born in Denmark between 1900 and 1910, the left-handed twin died first in 51 cases.

Why so long ago? Because they wanted to be sure both twins had died by the time of the study.

Design and carry out a hypothesis test for a systematic influence of handedness on lifespan. Interpret your findings.