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October 8th, 2012, 11:12 PM   #1
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Help with probability

Hi guys, can anyone help me with these stat questions please.

1. The Boston Bruins play in the Northwest Division of the Eastern Confer-
ence in the National Hockey League. For each game played against another
team in the Eastern Conference, the division[Atlantic(A), Northeast(N), or
Southeast(S)] and the outcome[win(W), loss(L), tie(T), or overtime loss(O)]
are recorded. Consider the following events.
E = The opponent is in the Southeast Division.
F = The Bruins win the game.
G = The opponent is in the Northeast or the game is an overtime loss.
H = The Bruins lose and the opponent is from the Atlantic Division.
a. Carefully sketch a tree diagram to illustrate the possible outcomes for
this experiment.
b. Find the sample space for this experiment.
c. Find the outcomes in each of the events E, F, G and H.
d. List the outcomes in E U F,F U G and H'
e. List the outcomes in E U H', E U F U G' and F U G' and F U G'

2. The germination rate for the pumpkin seeds is directly related to the
prevaling weather conditions. The Autumn Gold Pumpkin is medium-sized
and ripens to a deep orange. If conditions are seasonable, the probability of
germination is 0.85. If it is dry, suppose the probability that a random seed
will germinate is 0.75. Recent weather history suggests there is a 40% chance
of a dry start to the growing season. Suppose an Autumn Gold pumpkin seed
is randomly selected.
a. What is the probability that the growing season will be dry and the seed
will germinate?
b. What is the probability that the seed will germinate?
c. Suppose the seed did not germinate. What is the probability that the
growing season had a dry start?
3. Customers at a Safeway grocery store in Scottsdale, Arisona can pay for
purchases with cash, an ATM card, or a credit card. Fifty-ve percent of all
customers use cash and 38% use an ATM card. Careful research has shown that
of those paying with cash, 75% use coupons; of those using an ATM card, 35%
use coupons; and of those using a credit card, only 10% use coupons. Suppose
a customer is randomly selected.
a. What is the probability that the customer pays with a credit card and
does not use coupons?
b. What is the probability that the customer does not use coupons?
c. If the customer does not use coupons, what is the probability that he or
she paid with an ATM card?
4. While the temperature range of most household ovens is approximately
200-600 oF, most customers only use four or ve common setting. Suppose the
1
probability distribution for the oven temperature setting for a random selected
use is given in the table below.
x 300 325 350 375 400 500
p(x) 0.04 0.205 0.40 0.075 0.20 0.08
a. Find the mean, variance, and standard deviation of the oven temperature
settings.
b. Suppose three dierent uses are randomly selected. Find the probability
that the temperature settings for all three are at least 400 oF.
c. Supppose three dierent uses are randomly selected. Find the probability
that exactly one use is for 350 oF.
5. A commuter train from Long Island to New York City is scheduled to
arrive at 8:07 A.M. every weekday morning. The probability that the train
arrives on time is 0.90. Suppose 20 weekdays are randomly selected.
a. Find the probability that the train will arrive on time on at most 15 days.
b. Find the probability that the train will arrive on time on at least 12 days.
c. Find the expected number of days that the train will arrive on time.
d. Suppose the train arrives on time on at least 15 days. What is the
probability that it arrives on time on all 20 days?
math67 is offline  
 
October 9th, 2012, 09:19 PM   #2
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Joined: Aug 2012

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Re: Help with probability

Hey math67.

Can you show us what you have tried? We can't give you help without seeing what you've tried and what you are thinking as well as any other ideas you have related to the problems.
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