:3. First-born children are less likely to become alcoholic than are later-born children. A psychologist wonders whether this fact is also true of birth order within pairs of twins. To study this, he finds 8 pairs of twins (of suitable age) who volunteer to provide him with data on their drinking habits. He gathers this data for a month, and then computes the average daily ingestion of alcohol for each twin. Here are the results

Alcohol ingested (in ounces)

1st born 2nd born

1 4 5 2 0 3 3 1 2 Twin pair numbers 4 ! 0 1 !I 5 5 4 6 3 5 7 4 5 8 1 0

(For instance, the 1st born member of twin pair 1 had a average daily intake of 4 ounces of alcohol, while the 2nd born had an average daily intake of 5 ounces.) The null hypothesis is that, on the average, birth order does not affect alcohol intake. The alternative hypothesis is that, on the average, the 1st born member of a pair of twins tends to drink less than the 2nd born member. Suppose it is not true that the differences in alcohol intake have a histogram which follows the normal curve. Then a statistical test based on Student's t-distribution is invalid. There is, however, a statistical test you can use. Its P-value in this case is a. the chance that in 8 tosses of a fair coin you get no heads

b. the chance that in 8 tosses of a fair coin you get 1 or fewer heads

c. the chance that in 8 tosses of a fair coin you get 2 or fewer heads

d. the chance that in 8 tosses of a fair coin you get 3 or fewer heads

e. the chance that in 8 tosses of a fair coin you get 4 or fewer heads