# ugh...anyone wanna offer me some quick Statistics help?

#### pg22

##### Platinum Member
Hey,

This damn Stats course is the last class holding me back from finishing my UC transfer requirements so I can hopefully transfer to UCLA or UC Berkley. I'm working my ass off since math really isn't my thing, but some things are just killing me. Being as I don't have class untill Tuesday, nor have a tutor (trying to save some money but I may just have to bite the bullet) I'm resorting to AT . This may be really simple, but I'm just not getting it:

Assume the z scores are normally distributed w/ a mean of 0 and a standard deviation of 1.

If P(0 < z < a) = .3907, find a

There are others, but I'm hoping if someone can help me with this, I can get the rest. Thanks in advance

#### amnesiac

##### Lifer
Heh. Just took stats last year. Blech.
BRB while I go see if my Stats manual is around here.

#### pg22

##### Platinum Member
Thanks man, I appreciate it

Wanna know what's even worse? I took this stats class as a 6 week course :Q

#### amnesiac

##### Lifer
Originally posted by: pg19
Thanks man, I appreciate it

Wanna know what's even worse? I took this stats class as a 6 week course :Q

I took mine as a 4-week summer course. :Q :Q :Q

Ok well I couldn't find my textbook but IIRC you need a chart listing the Z values.

And are you sure you transcribed that problem correctly? It looks like something's wrong with it...

#### z0mb13

##### Lifer
If I am not mistaken :

P(0 < z < a) = .3907

Theta((a- 0)/ 1) - Theta((0 - 0)/ 1) = .3907 ..............

Theta((a- 0)/ 1) - 0.5 = .3907

Theta((a- 0)/ 1) = 0.8907

look at the normal table and find which theta value to be 0.897

then solve for a

#### pg22

##### Platinum Member
<FONT face=Verdana size=1>amnesiac - I do have a chart with Z values and yep, I did write the problem down correctly.

z0mb13 - I have to admit, I have the absolute slightest clue as to what you just wrote to me....

Here's another one:

If P(-b < z < b) = .8664, find b

I can't even tell you how much this is making me fume :disgust:</FONT>

#### pg22

##### Platinum Member
Sorry about the "font" tags..I'm using the WYSIWYG form and I have no clue how to get rid fo them...

#### z0mb13

##### Lifer
Originally posted by: pg19
<FONT face=Verdana size=1>amnesiac - I do have a chart with Z values and yep, I did write the problem down correctly.

z0mb13 - I have to admit, I have the absolute slightest clue as to what you just wrote to me....

Here's another one:

<EM>If P(-b < z < b) = .8664, find b

</EM>I can't even tell you how much this is making me fume :disgust:</FONT>

what I did was changing the equation to the Z values

if you have something like this

P(a < x < b)

is equal to

Z((b - mean)/sd) - Z((a - mean)/sd)

I think this is called normalization... or whatever

whats the mean and sd for the second prob?

#### z0mb13

##### Lifer
Also what I mean by theta is the Z value

#### TuxDave

##### Lifer
I think you definitely need a z-table for that, I think that's what it's called. If you find that, there's probably instructions on the next couple of pages to explain how to use it.

-Dave-