Stupid Stats!

[maziwanka]

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

if the probability tables you are consulting are of the form P(x<X)...

 

[TuxDave]

Originally posted by: Aquaman
THe answer is always 47 or C

Cheers,
Aquaman

Originally posted by: Nutdotnet

Here are the four possibilities:
0
0.168
0.268
0.368

Thanks in advance!

Originally posted by: iamme
ok, i got the answer.....it's 0.268

i'll post the work in a sec.

No way... Aquaman's strategy actually works?

 

[iamme]

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

the mean is 0.0976 not 0.976, but you've got it

 

[Nutdotnet]

Originally posted by: maziwanka

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

if the probability tables you are consulting are of the form P(x<X)...

Sorry, I'm not quite sure what that means.

 

[Nutdotnet]

Originally posted by: iamme

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

the mean is 0.0976 not 0.976, but you've got it

Yeah, .0976.


THANKS EVERYONE WHO HELPED!!!

 

[iamme]

Originally posted by: Nutdotnet

Originally posted by: maziwanka

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

if the probability tables you are consulting are of the form P(x<X)...

Sorry, I'm not quite sure what that means.

you have to understand what the value is that the table is giving you.

for example, my table gave me the value of 0.2324 from the 0.62 z-score. that means that's the area from the mean to X(0.0976 to 0). the area is equal to the probability. however, you're looking for the probabilty of x<0. so you'd have to subtract 0.5 - 0.2324 = 0.268.

try drawing the curve...it's easier to understand that way.

 

[DrPizza]

I'd love to help and frequently provide math and science help, but I hated stats (although it was a very easy A for me). I've tried (successfully) to empty my mind of the subject.

 

[Nutdotnet]

Originally posted by: iamme

Originally posted by: Nutdotnet

Originally posted by: maziwanka

Originally posted by: Nutdotnet

Originally posted by: maziwanka
you want the p(x<0). so the z statistic you seek has x=0, mean=expectation, and you have the SD. go from there.

Ahh..

So would it be this?-

z = ((0-.976)/.1568)

which would give me- -0.62244898 for Z

Probability would be- 0.266823281

if the probability tables you are consulting are of the form P(x<X)...

Sorry, I'm not quite sure what that means.

you have to understand what the value is that the table is giving you.

for example, my table gave me the value of 0.2324 from the 0.62 z-score. that means that's the area from the mean to X(0.0976 to 0). the area is equal to the probability. however, you're looking for the probabilty of x<0. so you'd have to subtract 0.5 - 0.2324 = 0.268.

try drawing the curve...it's easier to understand that way.

Thanks, that makes sense...except one really dumb question, and I think I already know the answer. Where do you get the .5 from?