Regression Predictions

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jpSartre
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Regression Predictions

Postby jpSartre » Fri May 28, 2010 7:03 pm

I ran a regression on my PTs over time, and the trend predicts a 172 come test day. Anyone interested enough to compare?

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voice of reason
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Re: Regression Predictions

Postby voice of reason » Fri May 28, 2010 7:55 pm

What is the standard error of the estimate?

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jpSartre
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Re: Regression Predictions

Postby jpSartre » Fri May 28, 2010 8:02 pm

2.6. It's been a while since econ stats... does that mean 172 +/- 2.6, are there degrees of freedom involved or am I confusing topics entirely?

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mountaintime
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Re: Regression Predictions

Postby mountaintime » Fri May 28, 2010 8:14 pm

my 172 turned into a 168 on test day :cry:

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voice of reason
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Re: Regression Predictions

Postby voice of reason » Fri May 28, 2010 8:24 pm

jpSartre wrote:2.6. It's been a while since econ stats... does that mean 172 +/- 2.6, are there degrees of freedom involved or am I confusing topics entirely?


Once you have a standard error calculated you don't have to think about degrees of freedom anymore.

It means the 95% confidence interval for the predicted score on your next practice test is 167 to 177 (172 +/- 2.6*1.96). In other words, if 100 people had the same practice record as you, then 95 of them would get a score in the range of 167 to 177 on the next test.

In practice the band may be narrower than that, because the test is designed to be a reliable measure of latent ability. To be sure I'd have to think more carefully about the statistical theory than I want to on a Friday night.

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jpSartre
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Re: Regression Predictions

Postby jpSartre » Fri May 28, 2010 11:15 pm

voice of reason wrote:
jpSartre wrote:2.6. It's been a while since econ stats... does that mean 172 +/- 2.6, are there degrees of freedom involved or am I confusing topics entirely?


Once you have a standard error calculated you don't have to think about degrees of freedom anymore.

It means the 95% confidence interval for the predicted score on your next practice test is 167 to 177 (172 +/- 2.6*1.96). In other words, if 100 people had the same practice record as you, then 95 of them would get a score in the range of 167 to 177 on the next test.

In practice the band may be narrower than that, because the test is designed to be a reliable measure of latent ability. To be sure I'd have to think more carefully about the statistical theory than I want to on a Friday night.


Haha, understandable. I appreciate the explanation.

I've got 3 tests left so well see if I can't bump that confidence interval up.




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