hi,

need some help on these stats problems:

1. the senior management of a corporation has decided that in the future, it wishes to divide its advertising budget between two agencies.
eight agencies are currently being considered for this work. how many different choices of two agencies are possible?

2. an analyst was asked to evaluate earnngs prospects for seven corporations over the next year and to rank them in order of predicted earnings growth rates.

(a) how many different rankings are possible?
(b) if, in fact, a specific ordering is simply guessed, what is the probability that this guess will turn out to be correct?

thanks :)

1. the senior management of a corporation has decided that in the future, it wishes to divide its advertising budget between two agencies.
eight agencies are currently being considered for this work. how many different choices of two agencies are possible?

total number of combinations of 2 companies out of 8 companies is 28 [8C2 = (8*7)/(1*2)]



2. an analyst was asked to evaluate earnngs prospects for seven corporations over the next year and to rank them in order of predicted earnings growth rates.

(a) how many different rankings are possible?
(b) if, in fact, a specific ordering is simply guessed, what is the probability that this guess will turn out to be correct?



You have answered (a) in (b). the probability that this guess will turn out to be correct depends on the probability of the predicted earnings growth rates in turn.

2. (a) 7! combinations are possible. 7! = 7x6x5x4x3x2x1 = 5040

2. (b) Probability is, of course, 1/5040.

Aren't you familiar with permutations and combinations?

im stuck on this problem:

the yankees playa series of five games against the boston red sox. for any one game, it is estimated that the probability of yankees win is .4. the outcomes of the five games are independent of one another.

a. what is the probability that the yankees will win a majority of the five games?

b. what is the probability that the yankees will win all five games?

c. if the yankees win the first game, what is the probability that they will win a majority of the five games?

d. before the series begins, what is expected number of yankees' wins in five games?

e. if the yankees win the first game, what is the expected number of yankees' wins in five games?

Don't just ask for answers!

Learn about Bernoulli (sp?) random variables. These are random variables that are either 1 or 0 / Yes or No / Success for Fail.

let n be the number of trials, in this case 5.
p = sucess rate = 0.4
q = failure rate = 1 - p = 0.6

The chance of getting a certain number of successes is writen as P(x).

Example: What is the probability of 2 successes?

A particular combination of two wins and 3 loses might be WWLLL. The chance of that is indentical to WLLWL if the games are unrelated. We want the chance of ANY 2 W 3L combination. Therefore, P(2) = number of combinations * chance of any one.
= nCx* (x^p)((n-x)^q)= 5C2 * 0.4*0.4*0.6*0.6*0.6

nCr forumla is "n!/(r!.(n-r)!)" and is a function on most scientific calculators.

This is much easier than appears in nasty text form, so write it out and try it.

a) 3,4 or 5 victories. Easlier to work out 1 - P(1) - P(2).
b) P(5), very easy.
c) 1 - P(1) P(2), but for 4 trials.
d) np (n = trials, p = sucess rate)
e) (n-1)p + 1 So exaclty the same, but for four trials - then add the first victory.

the following problems i have trouble solving, please help: :)

each member of a random sample of 15 analysts was asked to predict the rate of inflation for the coming year. assume that the predictions for the whole population of analysts follow a normal distribution with the standard deviation 1.8%.

a) the probability is .01 that the sample standard deviation is bigger than what number?

b) the probability is .025 that the sample standard deviation is smaller than what number?

c) find any pair of numbers such that the probbility that the sample standard deviation lies between these numbers is .90.


a medicine company produces pills containing an active ingredient. the company is concerned about the mean weight of this ingredient per pill, but it also requires that the variance be no more than 1.5. a random sample of 20 pills is selected, and the sample variance is found to be 2.05. how likely is it that a sample variance this high or higher would be found if the population variance is in fact 1.5? assume that the population distribution is normal.
:confused:

thanks.

i can use another helkp with this problem, driving me nuts all day long:

montly rates of return on the share of a stock are independent of one another and normally distributed with a standard deviation of 1.7. a sample of 12 months is taken.

a) find the probability that the sample standard deviation is less than 2.5.

b) find the probability that the sample standard deviation is bigger than 1.0.

thanks

I too have got a lot of assignments in statisitics. I'm beginning to think I should follow squid's example and post them here and make others do them for me!

anyone want to help me out? :)

What have you got so far, sqiud?

0 :)