[Casey]

Can anyone please help me with this?!?!?

[Jeff]

Originally Posted by Casey

Can anyone please help me with this?!?!?

yes. I can.

For the first problem, first notice that the events are not independent, since P(R) * P(C) is not equal to P(R and C). This means that you can't use multiplication rule, and that P(R)=/=P(R|C). It's also the answer to letter d.

For the answer to letter a, draw a tree diagram, with the probability of a recession as the first branch and the other branches being whether or not there is a competing product in each case. It will look like attached figure J.1

Notice that P(R and C) is .25, which is one terminating end of our tree diagram, J.1

To find P(C|R) we remember that P(R) * P(C|R) = P(R and C), which describes the idea of conditional probability. Simply solve for P (C | R). that is, .25/.4

for letter b, we simply reverse the positions of the letters on the tree diagram like shown in diagram J.2

To find P(R|C), remember that P(C) * P(R | C) = P (R and C) and the process is similar the that for letter a. Solve like this: .25/.5

(it seems as if a recession occuring will affect whether or not a competing firm puts out a product, but that the competing firm producing does not affect whether or not there will be a recession. Makes sense, eh?

letter c calls for a venn diagram, drawn as in figure J3. Simply figure out the probabilities for each outcome that the problem lists (one, the other, and both) and add them together: .15+.25+.25= .65


We haven't done problems two or three yet in my class, but I'll take a look and post back later if I have a conclusive answer.

[Jeff]

I think the answer to number II is $7.25 and no it's not fair, but I don't really know the definition of "expectation" I just multiplied the probability of each outcome times the amount and added it up together.

[Casey]

And just to be clear, the "|" means "and"?

[Casey]

oh and I already know number 3. shoud've saif that. heh. Thanks!

[Casey]

so...

[Jeff]

Originally Posted by Casey

so...

no no no no no non no no no n on o n

the | means

"given the information that"

the middle probabilities that go on the blanks are what your questions asks for :

the probability of C given R and the probability of R given C

[Casey]

Originally Posted by Jeff

no no no no no non no no no n on o n

the | means

"given the information that"

the middle probabilities that go on the blanks are what your questions asks for :

the probability of C given R and the probability of R given C

I see... I included the answer for a as the first answer for b.

[Casey]

1. A Super Market Manager has determined that the amount of time customers spend in the supermarket is approximately normally distibuted with a mean of 45 minutes and a standard deviation of 6 minutes. Find the probability that a customer spends between 39 and 43 minutes in the supermarket.

Ok so if I drew the normal distribution, 45 mins at the center... I have no idea what to do next.

2. Random Samples of size 2 are selected from the finite population which consists of the number 4, 7, 13, 16, and 19.
a. Find the mean and SD of this pop.
(I have no idea how to find the SD... wait, it's a formula or something right? Sigma^2=something.)
b. List the 15 possible random samples of size 2 that can be selected from the finite population and calculate their means.
(No clue how to do this one... really)
c. Construct the sampling distribution of the mean for the 15 possible random samples of size 2 from the given finite population.
(Same as b)

Thanks!
CAse