Editor:
This is in response to Steven Weeks' ("Beware of squirrels, fetuses and 'Big Lie,'" Sept. 15, 1995) comment. Steve, you are the one that is producing misleading statements to women. The implications of your comments about the probability of a woman getting raped once in five years being 5/6 (given the probability of a woman getting raped once a year is 1/6) is that if a woman stayed in school six years the probability of getting raped would be 6/6 or for certain.
The actual probability of a woman getting raped once in five years is not 5/6 (actually it is not even close!). I will demonstrate how to calculate the true probability. Suppose that the information provided that the probability of a woman getting raped in one year's time is actually 1/6. Then the probability of her getting raped once in five years will be binomially distributed, with n=5, x=1, p=1/6 and (1-p)=5/6; where n is number of years, x is number of times a woman is raped in five years, p is the probability of getting raped in one year and (1-p) is the probability of not getting raped in one year. We can use the following formula:
Probability of getting raped x times in n years:
Using this formula, we get the simple answer that the probability of a woman getting raped once in five years is 40 percent Ÿ well below the 5/6, 83.3 percent. Just to satisfy everyone's interest, to find out the probability of a woman getting raped two or three times in five years is just as easy. Just let x=2 or 3 ... Therefore the probability of a woman getting raped three times in five years is 3.2 percent.
Remember, these are statistical probabilities and each woman can take simple precautions to greatly reduce the chances of getting raped while in college or anywhere else.
Eric Schorvitz
Economics Ph.D. Student