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 Science, Math, and Philosophy Discussions regarding science, math, and/or philosophy.

 06-22-2012, 04:01 AM #3106 grinder     Join Date: May 2012 Posts: 479 Re: The Official Math/Physics/Whatever Homework questions thread I think this is a super simple question, but I want to be 100% sure. For each of the following combinations of n and p, find the mean of the sampling distribution of the sample proportion Phat. (Round your answer(s) to 3 decimal places.) A) n = 100; p = 0.4 E(Phat) = _________ B) n = 200; p = 0.94 E(Phat) = _________ C) n = 2000; p = 0.08 E(Phat) = _________ a) .4 b) .94 c) .08 correct?
 06-22-2012, 06:05 AM #3107 Pooh-Bah     Join Date: Feb 2009 Posts: 4,635 Re: The Official Math/Physics/Whatever Homework questions thread what's "phat"?
 06-22-2012, 11:39 AM #3108 grinder     Join Date: May 2012 Posts: 479 Re: The Official Math/Physics/Whatever Homework questions thread p-hat
 06-22-2012, 12:41 PM #3109 Carpal \'Tunnel     Join Date: Sep 2005 Location: Berkeley Posts: 13,706 Re: The Official Math/Physics/Whatever Homework questions thread I find it interesting that most of the statistics questions assume we know their notation and they don't want to define what anything is.
 06-22-2012, 01:33 PM #3110 grinder     Join Date: May 2012 Posts: 479 Re: The Official Math/Physics/Whatever Homework questions thread so expected value of p-hat. I'm not sure if it's whether they want .94 or 200*.94=188 for all of them. Last edited by kingofsurvivorbb; 06-22-2012 at 01:41 PM.
06-25-2012, 12:56 AM   #3111
Pooh-Bah

Join Date: Jun 2009
Posts: 5,862
Re: The Official Math/Physics/Whatever Homework questions thread

Quote:
 Originally Posted by Cueballmania I find it interesting that most of the statistics questions assume we know their notation and they don't want to define what anything is.
My high school statistics course was all about being able to repeat textbook examples with different numerical values. You didn't actually have to understand anything at all to get 90%+.

 06-25-2012, 06:28 PM #3112 newbie   Join Date: Feb 2012 Posts: 47 Re: The Official Math/Physics/Whatever Homework questions thread how do you get the answer for this problem, show work A password consists of four letters followed by three digit number. A) How many passwords are possible if there are no restrictions answer: 456,976,000 B) How many passwords are possible if none of the letters or digits can be repeated? answer: 258,336,000
 06-25-2012, 06:48 PM #3113 Carpal \'Tunnel     Join Date: Sep 2005 Location: Berkeley Posts: 13,706 Re: The Official Math/Physics/Whatever Homework questions thread How many letters are there? How many numbers? How do you find the probability of independent things?
 06-25-2012, 07:13 PM #3114 newbie   Join Date: Feb 2012 Posts: 47 Re: The Official Math/Physics/Whatever Homework questions thread 26 letters, 10 numbers
06-25-2012, 10:05 PM   #3115
old hand

Join Date: Jul 2007
Location: Losing at Omahaha
Posts: 1,486
Re: The Official Math/Physics/Whatever Homework questions thread

Quote:
 Originally Posted by asd16 26 letters, 10 numbers
Here's another hint. If it was one letter and one number in the password and you had to find how many combinations was possible, you would count them by saying: for each of the 26 letters, there are 10 numbers. I.e. for A there is 0,1,2...,10. Same for B, C,...

So, total number of combinations is 26*10 = 260.

Now, apply the thinking to your own problem.

 06-26-2012, 12:21 AM #3116 adept     Join Date: May 2008 Location: increasing potential GDP Posts: 1,170 Re: The Official Math/Physics/Whatever Homework questions thread Here's yet another hint. People don't respond so well when you say: "Here's a problem. Solve it for me and show your work." Try as best as you can and let us know where you get stuck. First, show your work.
06-26-2012, 08:44 AM   #3117
Carpal \'Tunnel

Join Date: Mar 2007
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Re: The Official Math/Physics/Whatever Homework questions thread

Quote:
 Originally Posted by non-self-weighter Here's yet another hint. People don't respond so well when you say: "Here's a problem. Solve it for me and show your work." Try as best as you can and let us know where you get stuck. First, show your work.
Yeah, some regs in this thread are more tolerant of this than others (I think I vary from day to day). But this isn't a "do my homework for me" thread. It's a "help me with my homework" thread.

We want to see your ideas and thought processes so that we can help you understand how to do the problem.

 06-26-2012, 09:20 AM #3118 old hand     Join Date: Feb 2010 Location: Germany Posts: 1,322 Re: The Official Math/Physics/Whatever Homework questions thread Hey, I've got this problem from my calculus 2 class. is the equiation x^y=y^x solvable after one of the variables around the points (e,e), (2,4)? I don't have any idea what to do here. I mean I can see that those two are obvious solutions, cause any x=y is a solution and another one would be (-2,-4), but that doesn't really help me We just did constrained extremums and inverse functions if that helps.
06-26-2012, 09:38 AM   #3119
Carpal \'Tunnel

Join Date: Mar 2007
Location: Redoubling with gusto
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Re: The Official Math/Physics/Whatever Homework questions thread

Quote:
 Originally Posted by Sven2812 is the equiation x^y=y^x solvable after one of the variables around the points (e,e), (2,4)?
I don't even know what this sentence means.

06-26-2012, 10:04 AM   #3120
old hand

Join Date: Feb 2010
Location: Germany
Posts: 1,322
Re: The Official Math/Physics/Whatever Homework questions thread

Quote:
 Originally Posted by Wyman I don't even know what this sentence means.

lol english is tough
ok we got x^y=y^x

so now we wanna write the equation in terms of:
x=f(y) or y=f(x)

but not everywhere just in a small area around (e,e) and (2,4)

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