# Effienciency and Alternative-Specific CBC Design

Good morning.
We are designing a CBC model using the Advance Module. Our design is the following:
Attribute 1: 3 levels
Attribute 2: 7 levels
Attribute 3: 5 levels
Attribute 4: 4 levels
Attribute 5: 7 levels  (Primary Attribute) When only one of its levels appears, Attribute 6 and 7 must not be displayed.
Attribute 6: 5 levels  (Conditional Attribute)
Attribute 7: 4 levels  (Conditional Attribute)
Attribute 8: 2 levels
We want to carry out a CBC model in paper and pencil, using 5 versions of cards with 9 concepts in each and 3 tasks for concept.
Our question is the following: When we define that the level that makes that Attributes 6 and 7 are not displayed is the first level of A5 (A5.L1), the efficiency test gives us results that are really different from the ones obtained if the level that makes attributes 6 and 7 not be  displayed is the last one  (A5/L7) and we donâ€™t know the reason why. Please, could you help us to understand that?

Efficiencies when level is the first one of A5:

Attr.    Level    Freq.    Actual    Ideal    Effic.
5    1    11    (this level has been deleted)
5    2    21    0,5182    0,3651    0,4965
5    3    21    0,5091    0,3651    0,5144
5    4    20    0,5349    0,3651    0,4661
5    5    21    0,5034    0,3651    0,5261
5    6    21    0,5158    0,3651    0,5012
5    7    20    0,5163    0,3651    0,5002

Efficiencies when level is the last one of A5:

Attr.    Level    Freq.    Actual    Ideal    Effic.
5    1    21    (this level has been deleted)
5    2    21    0,3578    0,3651    1,04180
5    3    21    0,3585    0,3651    1,03770
5    4    21    0,3584    0,3651    1,03800
5    5    21    0,3611    0,3651    1,02240
5    6    20    0,3686    0,3651    0,98160
5    7    10    0,5212    0,3651    0,49070
asked Feb 22, 2016

## 1 Answer

0 votes
Please don't use the "Quick Test" to look at design efficiencies...especially for alt-spec designs!  Look at the Quick Test only for level frequencies.  (In a future version of the software we're going to get rid of the Quick Test since it is not as useful or accurate as the Advanced Test, especially with alt-spec designs).

Use the "Advanced Test" (under Design Tab + Test Design + Advanced Test...).

--Bryan
answered Feb 22, 2016 by Platinum (198,715 points)