statistics help needed

It is getting confusing. Write down exactly what you turned in or make sure it said
5*.13*.87^4 = .37238...
Unless he is nitpicking and wants
5!/(1!*4!)(.13)^1*(.87)^4 = .37238...
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Gene
 
Yep, that is exactly what I turned in. My answer was .372 though. I didn't show that much after the decimal point. Maybe he is nitpicking. I can try turning it in the other way but wouldn't that just be stupid of him? If I have the answer and an acceptable formula it should be accepted.
 
I absolutly agree! If the answer is correct (and we are all agreed that it is) it should be accepted no matter how you got to it. But you want credit for it and we are trying to think of any reason why it might not have been. I like "The book is wrong." best.
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Gene
 
Hello, natenatmom!

The only thing I can find that might be what he wants is this:

. . . \(\displaystyle \L p(x)\:=\:\frac{n!}{x!(n-x)!}\,p^xq^{n-x}\)

Would that work for this problem?
Click to expand...
It certainly would . . . That's exactly what everyone has been using.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

I find the wording of the problem to be quite disturbing.

. . There must be more parts to it, right?


It could have said: \(\displaystyle \,P(\text{0 tickets}) = 0.13,\;\;P(\text{some tickets}) = 0.87\)

. . Why include: \(\displaystyle P(\text{1 ticket}),\:p(\text{2 tickets}),\) . . . ?


Your teacher may be trying to include all that extra information . . . somehow.

. . I would love to hear his explanation!
 
Well there are 2 parts to the question but I already did part A. It lists the probabilities for 0, 1, 2, 3, and 4 like I said and then A is to find the mean and standard deviation and B says to find the probability that over the next 5 days he will issue no parking tickets on exactly one day. That's all it says, no other information.

I have a question that I'm still confused on though. When it's asking for something that happens 0 times on 1 day, is X going to be 0 or 1? It's 1, right?

I'm going to write it out again and show the part of the formula with ! in it. When I turned it in before, I had just skipped ahead and given him the 5(13)^1(.87)^4. Maybe if I show the original formula and all the steps, he'll let me have it. The weird thing is that he didn't say I just needed to show my work, he just said it was wrong and I needed to redo it.
 
Are you saying the he said the A part is correct, but the B part is not correct?
 
I think that it is safe to say that this is an odd question!
The part A is really rather involved!
Part B is trivial to say the least.
One would expect to use information from part A to do part B.
 
When it's asking for something that happens 0 times on 1 day, is X going to be 0 or 1? It's 1, right?

Yup, x is the number of days that it happens out of n days. It doesn't matter if it is asking about something that happens 3 times on 1 day out of n or 0 times on 1 day out of n. x is still 1.

BTW: X is a different variable than x. You shouldn't mix upper and lower case in talking about the same variable.
 
If it's a good idea, natenatmom might ask the teacher to go to our site and check out the rather lively discussion this has created. Maybe find out exactly why the problem was marked wrong. To just mark something wrong with no explanation why 'just ain't cool, man'.
 
Not a cool idea. He has been maligned rather thoroughly. Printing a few pertinent posts might be all right but I'm unsure how he would feel about this kind of "research" in any case.
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Gene
 
You all should find this interesting. I questioned the teacher on what was wrong with my answer and he said he was holding all questions til after Christmas. So in the meantime, I asked another math teacher to explain how to do this problem to see what he would say. Here is what he wrote down for me...

Y is a binomial random variable with parameters n=5 and p=.13. So, the probability distribution of Y is given by:

P(Y=y) = (5,y)* (.13^y)* (.87^[n-y]) for y=0,1,2,3,4,5

Since we are interested in particular in the probability of receiving no tickets on exactly ONE of the days, we are interested in P(Y=1), which is given by:

P(Y=1) = (5,1) * .13 * (.87^4) = .37

Big surprise! He has the same thing I turned it. I can't wait to hear my teacher's explanation for why he keeps marking me wrong.
 
It happens. Try not to be TOO confrontive.

I challenged a Math Teacher / Wrestling Coach for a friend of mine while I was in High School. It was not my class and the teacher/coach did not know me. I set up a pathway of increasingly subtle problems that would expose his error.

Upon realizing his error, he switched his stance from learning/teaching to simple hostility. His exact words were, "So, what are you, some kind of big hero?" At that moment, he being rather large in stature, I was quite uncomfortable that he was between me and the nearest exit.

Who says mathematics is not a contact sport?
 
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