01-10-2017, 03:43 AM

I am looking into getting a Prime and am currently playing around with the simulator. (I currently have an HP71B which which has a flaky keyboard - after 30 years or so, not bad!)

Anyway, I was trying my favorite function: Calculating the confidence interval of the mean. I had no problem calculating the interval from some sample data, and it agreed with my reference.

However, my reference is for a DOE class and they apply the formula using the "pooled" standard deviation. If you have a bunch of replicants of a response surface, you use all the points to calculate the standard deviation, while you use only the number of samples in your mean calculation (one portion of the response surface) for N.

So for example the example in the course, you have 11 degrees of freedom for the standard deviation and only 3 points for N. This tightens the interval considerably.

So is there any way to use a pooled standard deviation with more degrees of freedom than you might have points that calculated the mean?

Anyway, I was trying my favorite function: Calculating the confidence interval of the mean. I had no problem calculating the interval from some sample data, and it agreed with my reference.

However, my reference is for a DOE class and they apply the formula using the "pooled" standard deviation. If you have a bunch of replicants of a response surface, you use all the points to calculate the standard deviation, while you use only the number of samples in your mean calculation (one portion of the response surface) for N.

So for example the example in the course, you have 11 degrees of freedom for the standard deviation and only 3 points for N. This tightens the interval considerably.

So is there any way to use a pooled standard deviation with more degrees of freedom than you might have points that calculated the mean?