Does anyone know anything about statistics? ? ? ?
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From: Anaheim, CA
Originally Posted by SXYS2k' date='Jan 25 2009, 11:33 PM
hey thanks.. im still lost but you helped a lil. Its hard taking math in intersession especially if math isnt your thing.
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From: SoCal
Originally Posted by a_zepeda926' date='Jan 25 2009, 10:57 PM
statistics is different than any other math class ive ever taken. i honestly like math, but statistics kicked my ass, and i had to study pretty hard for it. just wait til you get more deep into it.. how long you been taking it so far?
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From: Yorba Linda, CA
Originally Posted by SXYS2k' date='Jan 25 2009, 10:33 PM
hey thanks.
Originally Posted by SXYS2k' date='Jan 25 2009, 10:33 PM
im still lost . . . .
Now what? Instead of grabbing 100 giraffes each time, you grab 1,000 giraffes each time (still 1,000 samples), or 10,000 giraffes each time, or 100,000 giraffes each time (still 1,000 samples). If you get up to 1,000,000 giraffes in each sample, all of the samples will be the same: the entire population. So all of the sample means will be the same, and they'll all be the population mean. Because they're all the same, the variance will be zero.
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From: Anaheim, CA
Originally Posted by SXYS2k' date='Jan 25 2009, 11:59 PM
its my 3rd week just 2 weeks to go and the course is done. Its all compressed so it makes it hard to learn it all fast. But i got it, just that its a new chapter and the book has no examples of that specific type of question
if its anything like the class i took it will surely get harder...
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From: SoCal
Originally Posted by magician' date='Jan 25 2009, 11:00 PM
You're welcome.
Suppose that you're trying to determine the average height of a population of one million giraffes. You randomly grab 100 giraffes, measure their heights, and compute the average (mean) of those 100 heights. Is that the average (mean) height of all 1,000,000 giraffes? Probably not. So you randomly grab another 100 giraffes and average their heights, and another 100, and so on. You end up with 1,000 samples, and an average height for each sample. You average those 1,000 average heights. Is that the average height of all 1,000,000 giraffes? Probably not. Will all of the samples have the same mean height? Probably not. So the mean of the sample distribution will probably be different from the population mean, and the variance of the sample distribution will be positive (i.e., not zero).
Now what? Instead of grabbing 100 giraffes each time, you grab 1,000 giraffes each time (still 1,000 samples), or 10,000 giraffes each time, or 100,000 giraffes each time (still 1,000 samples). If you get up to 1,000,000 giraffes in each sample, all of the samples will be the same: the entire population. So all of the sample means will be the same, and they'll all be the population mean. Because they're all the same, the variance will be zero.
Suppose that you're trying to determine the average height of a population of one million giraffes. You randomly grab 100 giraffes, measure their heights, and compute the average (mean) of those 100 heights. Is that the average (mean) height of all 1,000,000 giraffes? Probably not. So you randomly grab another 100 giraffes and average their heights, and another 100, and so on. You end up with 1,000 samples, and an average height for each sample. You average those 1,000 average heights. Is that the average height of all 1,000,000 giraffes? Probably not. Will all of the samples have the same mean height? Probably not. So the mean of the sample distribution will probably be different from the population mean, and the variance of the sample distribution will be positive (i.e., not zero).
Now what? Instead of grabbing 100 giraffes each time, you grab 1,000 giraffes each time (still 1,000 samples), or 10,000 giraffes each time, or 100,000 giraffes each time (still 1,000 samples). If you get up to 1,000,000 giraffes in each sample, all of the samples will be the same: the entire population. So all of the sample means will be the same, and they'll all be the population mean. Because they're all the same, the variance will be zero.
Thanks again.
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From: Disneyland
Originally Posted by SXYS2k' date='Jan 25 2009, 10:52 PM
haha. it was easy untill i ran into this crap. My teacher gives us take home test's over intersession and this is beating me up. Ive been at it for hours and i cant get this
but im not as smart as the other 2 ppl who just wrote in here.. cuz i have no idea what it says
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From: SoCal
Originally Posted by a_zepeda926' date='Jan 25 2009, 10:54 PM
if the sample size is larger, it becomes closer to what mu actually is (the actual mean). we can never know the actual mean of anything, that is just the nature of the world, but by increasing the sample size, we can get the closest estimate for mu (actual mean). hope this helps. haha sorry the the first post.. i just had to brag a little..
This one helped too. I put yours and the other one down for my answer so theres no way im getting this wrong now.haha
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From: SoCal
Originally Posted by mszalli' date='Jan 25 2009, 11:15 PM
lol same here cuz i actually like math.. but im not as smart as the other 2 ppl who just wrote in here.. cuz i have no idea what it says
but im not as smart as the other 2 ppl who just wrote in here.. cuz i have no idea what it says