[Kham]

quick how do you do this problem?

-----
The amount of snowfall falling in a certain mountain range is normally distributed with a mean of 74 in., and a standard deviation of 12 in. what is the probability that the mean annual snowfall during 36 randomly picked years will exceed 76.8 in.?

[ChrisNoF4i]

False!

[newgixxerchic]

76.8 -74 = 2.8
2.8/12 = z score
look at the amount on the z table
.5 - (.0910) = that number would be the probability that it was greater than 76.8

I think its 40.90% or .4090 (but don't quote me)

[JohnnyV]

teacher teacher Kham's trolling NESR for test answers!!!

[SVRACER01]

pretty good....thats my answer.

[Kham]

thanks Alicia. that's what i thought the #36 has nothing to do with the problem.

[Doc]

I was gonna say 38% but that was a guess. I like Headtilters answer better.

As to the how. 74in +/-12in of the 36 random years 1/2 would be in the plus catagory. Off those 18 years the number that would exceed 76.8 would most likely be more than half...

That is how I came to my guesstimate.

[Kham]

where's 18 yrs come from?

[newgixxerchic]

Originally Posted by Kham

thanks Alicia. that's what i thought the #36 has nothing to do with the problem.

no the whole point of the probability table is that each time you would estimate it would be independent of the next time....

like if you flip a coin, your chances are 50/50, no matter how many times you flip it.

[newgixxerchic]

Originally Posted by Kham

where's 18 yrs come from?

he's just being a smart ass...

good luck!

[Kham]

Originally Posted by newgixxerchic

76.8 -74 = 2.8
2.8/12 = z score
look at the amount on the z table
.5 - (.0910) = that number would be the probability that it was greater than 76.8

I think its 40.90% or .4090 (but don't quote me)

hold on!

i dont get the .5 - (.0910).
isn't it 1 - .591) = .409 , z score is .233 -btw which gives .591 area. same answer though.

[newgixxerchic]

yeah both ways are correct...

since half of the bell curve falls on one side of the curve and half falls on the other side you can either add .5 to the area and subtract that from one or you can subtract the area from .5 and it still measures the same amount of probability... hard to explain without drawing the bell curve and shading it in....

but since you're finding a probability for greater than a number rather than in between two numbers... both ways work....

[Kham]

i see. that explains .091. smart girl. thanks again.

that 36 threw me off. im just an average joe.

[ZX-12R]

Kham... Now I want to see you derive the integral.

[Kham]

Originally Posted by ZX-12R

Kham... Now I want to see you derive the integral.

oh good. now i know who to ask. that will be next couple semasters maybe.

[Doc]

Originally Posted by Kham

where's 18 yrs come from?

18 is half of 36.

[Kham]

CRAP! we were wrong. doc's right. 36 has to be accounted for. problem ask for "mean" not single value.

so z score = (76.8 - 74) / (12 / square root of 36) = 1.4

so 1 - P(Z > 1.4) = .9192 ==> 1 - .9192 = .0808 which is 8.08%

--> me

[Uncle Snake]

I do math for a livinng and I've got to go with

[Wishbone]

Is this NESR bazaro world?

[97BladeRider]

Who would've thunk it.....

knows something.

[Wishbone]

"Chuck Chuck Bo Buck"

[97BladeRider]

Originally Posted by fasterthanu

"Chuck Chuck Bo Buck"

You can thank Mr. Oreo for that one.

[Kham]

Originally Posted by 97BladeRider

Who would've thunk it.....

knows something.

i demand you give me credit.

hey Chuck, did you cut the plastic yourself to install the slider? how you do it?

[97BladeRider]

Originally Posted by Kham

i demand you give me credit.

hey Chuck, did you cut the plastic yourself to install the slider? how you do it?

That was credit. To be honest, I'm decent at math and I didn't get it.

And yes, I did cut the plastic myself for the sliders. Why do you ask? (yes it is slightly off)

[Kham]

Originally Posted by 97BladeRider

And yes, I did cut the plastic myself for the sliders. Why do you ask? (yes it is slightly off)

i show you what else i know cause i just did mine. how you do it?