Pedro,

I forget how many chances you get in corsi by default, but assuming it
is 2, what I think the traditional span score does is gives a number
for the level at which at least one set is recalled correctly. You are
suggesting a criterion for which both are recalled correctly.  Both of
these are poor and biased estimates of the 50% point on the memory
function. An unbiased estimate is the LD50 in logistic regression which
is my favorite way of measuring a span score, and I think the method we
use is also an unbiased estimate of this (but I don't have a
mathematical proof and I haven't thought about this hard since I was
working on my dissertation).  5.5 would indicate _either_ perfect
recall at length 5,  1/2 at length 6; and 0/2 at 7; or it could
indicate something like 2/2 at 4, 1/2 a 5, 1/2 at 6, and 1/2 at 7; 0/2
at 8. There may be some other ways to get that value as well.

You are free to score it however you want. The raw data is available
for each subject, and the report you got this from is just a simple way
to quickly get a number that is consistent across all users of PEBL.

Best,
Shane



On Mon, 2016-11-07 at 16:01 +0000, Pedro Rodrigues wrote:
>  
> Hello,
>  
> I’m conducting my PhD thesis and for this end I’m using the Corsi
> Block Test of the PEBL.
> However, I have a doubt about the results which the program give me.
>  
> Can you clarify me, please?
> For instance, a participant had the following results:
>  
> Last Item attempt to Complete:  6
> Total Score:          54
> Total Tentativas Correctas:               9
> Memory Span:          5.5
>  
> We can define “memory span” as span extension was established
> as the length of the last list recalled correctly (two attempts for
> each span length starting from 3 to a maximum of 9).
> If this participant failed one of the two attempts of the item with 6
> blocks, why was not memory span 5?
> In my interpretation, memory span is always an entire number or is my
> impression wrong?
>  
>  
> I look forward to hearing from you.
>  
> Best regards,
> _________________________________
> Pedro F. S. Rodrigues | PhD Student
> Psychologist nº: 15329 (OPP)
> University of Aveiro
> Depart. of Education and Psychology (C.1.51)
> Campus Universitário de Santiago
> 3810-193 Aveiro | Portugal
> Phone: (351) 234247144 ext. 24243
> Email: pedro.fil...@ua.pt
>  
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