Tuesday

September 23, 2014

September 23, 2014

Posted by **Sam** on Tuesday, December 8, 2009 at 11:03pm.

- Statistics -
**PsyDAG**, Wednesday, December 9, 2009 at 12:14pmThe p ≤ .01 (or some other value) is the criteria (cutting line) that you use to reject your null hypothesis. This means that the results you found would happen by chance only or less than 1 time in 100, and you are assuming that this is NOT that one time. However, the probability is still there, and you could be wrong (alpha error).

This is why experiments are replicated. Let's say that you have done the experiment three times and rejected the null hypothesis each time at P ≤. 01. What is the probability that you would have gotten the same results at that level all three times? It is .01^3 = .000001 = one time in a million. Although there might be one chance in a million of alpha error, I would be VERY confident in rejecting the null hypothesis.

Confidence levels indicate your confidence in an estimate (e.g., mean). 99% confidence level from a sample indicates that you are 99% sure from the sample that the true mean lies within that interval. (The larger the sample, the smaller — more specific — your estimate of the population mean will be.) However, there is still a 1% chance that the true mean will be outside that interval, but we assume that this is NOT the case.

I hope this helps you understand.

- Statistics -
**Sam**, Wednesday, December 9, 2009 at 7:27pmLet me see if I understand this:

----------------------------------------

null hypothesis: an observed difference is only due to chance - not because a particular variable affects another one

alternate hypothesis: an observed difference is due to one variable affecting another one, not because of chance

p value: the probability of getting a particular value assuming that the null hypothesis is true (if it's due to chance, then what is that chance)

If the p value is sufficiently low, that means we can reject the null hypothesis because the likely hood of getting a certain value merely by chance is so small that we can assume the null hypothesis was simply false to begin with.

----------------------------------------

^ Is all of that correct?

- Statistics -
**PsyDAG**, Thursday, December 10, 2009 at 11:12amSounds good!

**Answer this Question**

**Related Questions**

statistics - 1000 significance tests are performed using alpha = .05. Assumimg ...

Economics - What would be the economic implications for both exporting countries...

Statistics:Z and T Statistics: Confidence Interva - Z and T Statistics: ...

chemistry - what is the significance of partial molar enthalpy of mixing? I ...

statistics - A company director took a sample of salaries of 13 employees in a ...

STATISTICS - DEPENDENT MEANS OF EXPERIMENTAL GROUP OF 20, MEANS OF 38, STD 3, ...

com 150 - I have answered all of the questions and need help with some of the ...

Statistics - Tony’s father, an accountant, has been listening to Tony tell him ...

Statistics ! - Hi I have calculated some statistics using a spreadsheet program ...

Physics - A rotating door is made from four rectangular glass panes, as shown in...