Regression Predictions Forum
- jpSartre
- Posts: 326
- Joined: Sun Jan 03, 2010 11:05 am
Regression Predictions
I ran a regression on my PTs over time, and the trend predicts a 172 come test day. Anyone interested enough to compare?
- voice of reason
- Posts: 264
- Joined: Thu Oct 29, 2009 12:18 am
Re: Regression Predictions
What is the standard error of the estimate?
- jpSartre
- Posts: 326
- Joined: Sun Jan 03, 2010 11:05 am
Re: Regression Predictions
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?
- mountaintime
- Posts: 222
- Joined: Tue Sep 08, 2009 6:38 pm
Re: Regression Predictions
my 172 turned into a 168 on test day 

- voice of reason
- Posts: 264
- Joined: Thu Oct 29, 2009 12:18 am
Re: Regression Predictions
Once you have a standard error calculated you don't have to think about degrees of freedom anymore.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?
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.
- jpSartre
- Posts: 326
- Joined: Sun Jan 03, 2010 11:05 am
Re: Regression Predictions
Haha, understandable. I appreciate the explanation.voice of reason wrote:Once you have a standard error calculated you don't have to think about degrees of freedom anymore.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?
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.
I've got 3 tests left so well see if I can't bump that confidence interval up.
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