Statistics help!

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0123456789

Active member
so i have the zvalues, btu i need to find the p-values ising these. i know its kidna vague, but if anyone can help me out id be very greatful. pm me for more info on the problem.
if anyone wants to tell em how to find it thatd be great i cant find my notes eplainging it so thats pretty much all i need.
one more thing, if you know stats you probably know the bigass chart type thingy used for z values. do i just go to my z value(ie. 1.23) then find the corresponding value, and that corresponding value is my p-value?
thanks agian newschoolers, dont let me down!
 
gah, i need help on another problem as well. i need to find the 75th percentile for a normal distribution curve. pm me if you got the lowdown on how to do that.
 
Yeah I know what you are talking about.

Right now you only have Z scores?

I don't think you can find P with only a Z score.

Do you have standard deviation? or Alpha? How bout' n or a mean?

 
totally just did my homework for this chapter.... except i copied it. do you know the population standard deviation? if you do you gotta use the standard normal distribution table if you only know the sample standard deviation you gotta use the degrees of freedom table.
 
lets see for the first problem i have:z-scoremu(mean)std dev.
and i think thats it.
the only table i have from my book is the "areas under the standard normal distribution"

 
whats alpha? i dont think we learned that one yet. our teacher showed us how to do it but i didnt get the notes due to being absent
 
OH duh, my bad we did this in the start of the year.

Go to your Zscore table and find the corresponding number to your Z score.

That's your P value
 
im guessing since the only table he has is the standard normal he has the population standard deviation. or he doesnt see the other table in his book.
 
It should look like this:

Screen_shot_z-score.JPG


Just read across and find it.
 
sweet, thats what i thought. + karma to all

and i think i have the 75th percentile figured out. but ill post if i dont
 
Using another online Z table it came out to .8907 which is not statistically significant at any reasonable alpha level.

I am not sure you've gotten there yet.
 
Doesn't it matter if it's one tailed or 2 tailed?

I.e you are looking for either the top or bottom 25%, OR you could be looking for the probability it is either in the top 12.5% or the bottom 12.5%,. depending on the question
 
Ummm you can't be serious, you have to memorize values from -3.4 to 3.4?

I know they are related in terms of going up, but still that sucks!
 
The P-value is just the lowest level of significance that would lead to rejection of the null hypothesis.

There not really an equation for finding it, but it is the probability

found in either the z-table or t-table associated with either the

calculated z-value or calculated t-value.

For example, Suppose your calculated z-value is -1.86, your p-value is 0.0314. This is right out of the Z table
 
That'd be statistically significant at a .05 alpha level and you would reject the null hypothesis.
 
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