Assignment 2

Discussion

Rare events

Read the article DNA fingerprinting; it's a case of probabilities written by Richard Saltus for the Boston Globe and discuss the following questions.

1. Estimate the probability that you have an identical twin that you do not know about.
2. Estimate the probability that the DNA evidence in a randomly selected trial has been faked because someone involved wants to get a conviction.
3. Estimate the probability that someone else has the same social security number as you.
4. Estimate the probability that someone in the world has at least half of their chromosomes in common with you.

Enough, already

One way to avoid most of the nonsense associated with DNA fingerprinting would be to collect DNA fingerprints of everyone in the country. Then instead of speculating about whether certain genetic markers are independent within subpopulations, and all that hogwash, we can just check a DNA sample against everyone in the population.

• What, if anything, is wrong with this idea?

Why all the zeroes?

Say you're prosecuting a case where there is a DNA match. It occurs to you that you could ask your experts to testify, not that there is only a one-in-a-billion chance of this match, but rather that the chance is `real small', and while opinions differ about exactly how small that might be, nobody will contest that the chance is bigger than one in a hundred.

• How about it?

It depends

1. Do you think that women at Dartmouth are more likely to have blond hair than men? How could you decide this?
2. Name some pairs of characteristics of people that are likely to be independent.
3. Suppose you wanted to see if ``color of eyes" is independent of ``color of hair". How, using data from this class, could we try to determine this?

Homework assignments for Thursday September 29

• Read Chapters 1 and 2 of FPPA. Do the following review exercises at the end of Chapter 2 on Page 22: 1, 3, 5, 9, 12

Journal Assignment for Thursday September 29

Read, on Mosaic, DNA Typing: Statistical Basis for Interpretation Chapter 3 from the report of the National Reseach Council.