hi all, please can anyone help me
1. The internal auditing staff of an local manufacturing company performs a sample audit each quarter to estimate the proportion of accounts that are delinquent more than 90 days overdue. The historical records of the company show that over the past 8 years 13 % of accounts are delinquent. For this quarter, the auditing staff randomly selected 25 customer accounts. What is the probability the no more than 40 accounts will be classified as delinquent?
2. A PH.D graduate has applied for a job with two universities, A and B. the graduate feels that she has a 60% chance of receiving an offer from university A, and a 50% chance of receiving an offer from university B. if she receives an offer from university B, she believes that she has an 80% chance of receiving an offer from university A:
- What the probability that both universities will make her an offer?
- What the probability that at least one university will make her an offer?
question no.1 i didn't know to start
for the second question i solve it like this
p(A and B) = p(A) * p(A/B)= .6 * .8 = .48
p(A or B) = p(A) + p(B) - p(A and B) = .6 + .5 - .48 = .62 .... but i got zero
I would say the probability was zero because if you only surveyed 25 accounts you obviously can't find 40 accounts delinquent since 40 > 25For this quarter, the auditing staff randomly selected 25 customer accounts. What is the probability the no more than 40 accounts will be classified as delinquent?
Are you sure you provided all the information from the question?
"Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995
sorry 250 accounts
And for question 1 you might want to use the binomial distribution.
Well at least we found a case where p = o (in the original example)
"Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995
for 2 b
p(A or B) = p(A) + p(B) - p(A and B) = .6 + .5 - .40 = .7 right :$
Looks good to me.
Have you ever learn/heard of the Binomial distribution? If yes you should be able to know what kind of "experimental outcome" you can use it to model.
http://en.wikipedia.org/wiki/Binomial_distribution
Recently I have also tried to explain this once. Maybe you would take a look (#2) and answer the question posted.
http://www.talkstats.com/showthread.php/22084
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