choice-metrics.com

Thanks again.

I just need a confirmation on one thing..

You mentioned in the previous mails that "increasing the design also means that you will ....... efficiency per choice task will actually go down" & "that the D-error hasn't got much meaning".

I executed the most recent script shared by you for 2 scenarios and following were the results:

1. Rows=30; block=2; (which comprise of less efficient choice tasks) and the simulation stabilized at a D-error ~ 0.66

2. Rows=15 (which comprise of more efficient choice tasks than the former) and the simulation stabilized at a D-error ~ 1.33

So, should I still consider the second design to be more efficient even if the D-error is worse off than the first case? Please confirm.


Also, which metric helps us in deciding that the second design is more efficient?


Thanks
Neeraj

Thanks again.

I just need a confirmation on one thing..

You mentioned in the previous mails that "increasing the design also means that you will ....... efficiency per choice task will actually go down" & that the D-error hasn't got much meaning.

I executed the most recent script shared by you for 2 scenarios and following were the results:

1. Rows=30; block=2; (which comprise of less efficient choice tasks) and the simulation stabilized at a D-error ~ 0.66

2. Rows=15 (which comprise of more efficient choice tasks than the former) and the simulation stabilized at a D-error ~ 1.33

So, should I still consider the second design to be more efficient even if the D-error is worse off than the first case? Please confirm.


Also, which metric helps us in deciding that the second design is more efficient?


Thanks
Neeraj

Hi,

A gentle reminder regarding the query that I posted the last week.


Thanks
Neeraj

design 1 with 30 rows has D-error = 0.66, which means that the determinant of the AVC matrix is 0.66^4 = 0.189.
design 2 with 15 rows has D-error = 1.33, which means that the determinant of the AVC matrix is 1.33^4 = 3.129.

Scaling design 2 to 30 rows will yield an AVC matrix in which all elements are divided by 2. This means that the determinant of the AVC matrix with 30 rows will be (1/2)^4 * 1.33 = 0.195.
Then the D-error is 0.195^(1/4) = 0.665.
(if I did all the math correctly).

So in your case the efficiency of the choice tasks in the design with 15 rows is the same as the design with 30 rows.

Or to make the computation more simple, you can divide the D-error by half, 1.33 / 2 = 0.665.

Thanks a lot for explaining the concept..

I didn't come across the same in the Ngene manual.
Just a small correction to the mathematical calculation.

AVC matrix with 30 rows will be (1/2)^4 * 1.33 = 0.195. --> This should be AVC matrix with 30 rows will be (1/2)^4 * 3.129 = 0.195 (3.129 is the determinant of the AVC matrix for 15 rows)


Thanks
Neeraj

That is right, Thanks for the correction.