Psychology 315 - Probability exercises


1. Compute each of the following probabilities. Questions refer to throwing a fair die. Answers may be left in fractional form.
 
    a. The probability of throwing either a 2, 4, 5, or 6 on one throw.
 
    b. The probability of throwing either a 2 or 3, and then a 5.
 
    c. The probability of throwing a 3 and then a 14.
 
2. In the following problems cards are drawn from a standard 52-card deck. Before the next draw the card drawn is replaced and the deck thoroughly reshuffled. Compute each of the following probabilities.

    a. The probability of drawing a 10 on the first draw.
 
    b. The probability of drawing either a deuce, 3, 4, 5, heart, or a diamond on the first draw.
 
    c. The probability of drawing the ace of spades twice in a row.
 
    d. The probability of drawing either the seven of clubs, a jack, a ten, or a spade on the first draw, and then drawing either
         the ace of diamonds or nine of hearts on the second draw.
 
3. You ask your roommate to mail a letter. The probability that she will mail it is .98. The probability that the post office will fail to deliver it, given it was mailed, is .15. What is the probability that the letter will be mailed and the post office will fail to deliver it?
 
4. Assume that instead of replacing a card in the deck after it has been drawn, any card drawn on the 1st draw is thrown away.
 
    a. Recompute 2c under this new assumption.
 
    b. Recompute 2d under this new assumption.