The digit ratio is the ratio of the lengths of different digits or fingers typically measured from the midpoint of bottom crease where the finger joins the hand to the tip of the finger.It has been suggested by some scientists that the ratio of two digits in particular, the 2nd (index finger) and 4th (ring finger), is affected by exposure to androgens e.g. testosterone while in the uterus and that this 2D:4D ratio can be considered a crude measure for prenatal androgen exposure, with lower 2D:4D ratios pointing to higher prenatal androgen exposure.
From a study of 136 males and 137 females:
* Males: mean 0.947, standard deviation 0.029.
* Females: mean 0.965, standard deviation 0.026.
Assuming a normal distribution, the 95% confidence interval for average length is 0.889-1.005 for males and 0.913-1.017 for females.