oK WHAT am I doing wrong.

**Daredevilpwn** · 02-24-2013 10:32 PM

Here is a sample stat problem. I need to find E, the forumula for E is E = Zc * sqrt(p)(q)/n. For the question n = 900 p = .63 q = .37. And zc = 2.575. This plugged into forumula is E = 2.575 *sqrt(.63)(.37)/900. The answer, according to the book should be 0.041. What my issue is that when I put this in my calculator (ti-82) I get a totally different answer, that being 0.013. There are more decimal places but I dont feel the need to add them all. As you can see I am getting a completly different answer. I doubt the book is wrong but I don't know what the heck I am doing incorrectly, I tried plugging this into my calculator in many different ways and get the same result everytime. So someone please tell me what the heck is going on? I tried using a Ti-83 emu to see if I would get a different result, nope same answer.

**Xei** · 02-25-2013 10:25 AM

...because that formula is ambiguous. Even I can't tell you what the right answer is. Do you mean calculate p*q/n and then take the square root of it? Or do you mean calculate p*q, take the square root of it, and then divide by n? Calculators are not mind-readers, and the different ways of doing it will give you different answers. You need to use brackets.

**Daredevilpwn** · 02-26-2013 03:59 AM

Originally Posted by Xei

...because that formula is ambiguous. Even I can't tell you what the right answer is. Do you mean calculate p*q/n and then take the square root of it? Or do you mean calculate p*q, take the square root of it, and then divide by n? Calculators are not mind-readers, and the different ways of doing it will give you different answers. You need to use brackets.

This is how the book portrays the formula. formula.jpg And this is me plugging in the numbers. updated one.jpg

My answer shoild be 0.041 but somehow I am not inputting it correctly and I am just not sure how I am supposed to be using this formula. You can ignore the attached thumbnail, I uploaded that by mistake, it wasn't zoomed in enough.

**Xei** · 03-01-2013 10:09 AM

My advice still stands. How exactly does your book portray the formula? Because it won't be like that. Take a picture if you can. Is the letter N inside the square root symbol, or outside?

It doesn't matter either way, the way you're typing it in is still ambiguous. There's no way to tell what you're actually trying to calculate. Do you want to calculate (.63*.37)/900 and then square root it, or do you want to calculate (.63*.37), square root it, and then divide it by 900? These are not the same thing and will give you different answers, and currently the calculator can't tell what you mean and is having to guess, incorrectly. You need to use brackets to distinguish which one you mean. Can you do that? Do you understand how to use brackets?

**Alric** · 03-02-2013 02:47 AM

The book is wrong. Given the information you put it in correctly, but even if you put it in the other ways you still don't get the answer the book gives. I tried it every possible way I could think of and no way gives the answer the book listed. So either you wrote down the wrong numbers or the book is wrong. It wouldn't be the first time that a book is wrong.

**JoannaB** · 03-02-2013 03:41 AM

Sorry if this neither helps nor makes you laugh (I hope to achiev one or the other):

Have you considered lucid dreaming this problem, and asking an emu bird instead of the Ti-83 emu what the correct answer is? I remember when I used to lucid dream as a college student, I would sometimes try to resolve match problems in lucid dreams. Sadly the results that I arrived at using this method made very little sense upon waking up, but your results may be better.