Posted by
Mike on
Jul 15, 2016; 1:22pm
URL: http://spssx-discussion.165.s1.nabble.com/Non-Equivalent-Control-Groups-Design-Quasi-Experimental-Design-tp5732723p5732746.html
Not speaking for Kat but the following quote from one of his/her earlier
posts is relevant:
|As I did not randomly assign the participants to the groups for
|picture-viewing (I made sure each picture-viewing condition had
|equal no. of participants in each BMI classification), I think it
should
|not be considered as random assignment?
So, the questions are:
(1) How were subjects assigned to the 3x3=9 combinations.
They can't be assigned to BMI conditions, so random assignment
has to be done at the image viewing conditions.
(2) Bruce is correct and I was wrong in saying below that only
27 subjects were needed because there are 9 subjects (replications)
for each of the 9 cells, so 9x9=81 total subjects.
I took Kat at his word that the subjects were not randomly assigned
but perhaps how subjects were assigned to image conditions should
be made clearer (e.g., first 9 subjects in G1C1, second 9 subjects in
G1C2,
etc., or first subjects in G1C1, second subject in G1C2, etc -- I don't
think
one can reasonably argue that either of these assignments are random).
-Mike Palij
New York University
[hidden email]
----- Original Message -----
From: "Bruce Weaver" <
[hidden email]>
To: <
[hidden email]>
Sent: Friday, July 15, 2016 8:40 AM
Subject: Re: Non-Equivalent Control Groups Design/ Quasi-Experimental
Design
> The diagram in the original post shows (in an somewhat unconventional
> way) a
> 3 (weight groups) x 3 (treatments) table with 9 Ss per cell, so N = 81
> in
> total. I must confess that I haven't followed this thread that
> closely, but
> it seems to me the main question boils down to whether the 27 in each
> weight
> group were randomly allocated to the 3 treatments.
>
> Kat, apologies if I missed this earlier in the thread, but how did you
> allocate the 27 Ss within each weight group to the three treatments?
>
> HTH.
>
>
>
> Mike wrote
>> If collecting the data is not too difficult, I would suggest
>> replicating the experiment -- we are talking about N=27,
>> right? The key thing would be randomize the people in
>> the blocks across the images, following the example of
>> Allan Edwards that I provided earlier. The analysis would
>> be rather straightforward from there. Moreover, you could
>> compare the results from the first experiment to the second
>> experiment to see how much of a difference the randomization
>> makes in the results.
>>
>> It is possible that a source like Kirk or some other researcher
>> has analyzed a design like you have now and has figured out
>> a way to make sense of the data but this will entail a search
>> of the literature and evaluation of the methods. This could take
>> a fair amount of time unless someone knows for sure that there
>> is (or there is not) another way to analyze the data.
>>
>> The decision I think you have to make is which of the above
>> options will take less time to do.
>>
>> -Mike Palij
>> New York University
>
>
>
>
>
> -----
> --
> Bruce Weaver
>
[hidden email]
>
http://sites.google.com/a/lakeheadu.ca/bweaver/>
> "When all else fails, RTFM."
>
> NOTE: My Hotmail account is not monitored regularly.
> To send me an e-mail, please use the address shown above.
>
> --
> View this message in context:
>
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