Dear Chih-Hao,
You could test for 1) with a paired t-test.
2) and 3) are both testing for a group by condition interaction but they
will not give you identical results due to different pooled vs
partitioned error model. This has been discussed at length on this
mailing list and is described formally in this technical note:
http://www.fil.ion.ucl.ac.uk/~wpenny/publications/rik_anova.pdf
Best regards,
Guillaume.
On 12/01/17 08:26, 連 志浩 wrote:
> Dear Guillaume,
>
> Thanks for your helps.
>
> I want to make sure that all my contrast weights are right and whether
> the results from flexible factorial design and two sample t test are same.
>
>
> 1. To compare difference between 2 conditions in 1 Group, for example, I
> want to compare "G1C1 - G1C2".
>
> I guess the contrast weight would be [ 1 -1 0 0 0 0 0 0 zeros(1,18)
> zeros(1,8) ].
>
>
> 2. If I want to know the difference between Groups after both them
> compared "C1-C2", then the contrast weight should be [ 1 -1 0 0 -1 1 0 0
> zeros(1,18) zeros(1,8) ].
>
>
> 3. If I compare "C1-C2" for each group at 1st-level, then use these con
> img at two sample t test (2nd-level, Independence: Yes, Variance:
> Unequal), then input [ 1 -1 ] in vector to compare them.
>
> Would the result from this two sample t test be same with my second
> question?
>
>
> Best regards,
>
> Chih-Hao
>
>
>
>
> ------------------------------------------------------------------------
> *寄件者:* 連 志浩
> *寄件日期:* 2017年1月12日 上午 09:23
> *收件者:* Guillaume Flandin
> *副本:* [log in to unmask]
> *主旨:* RE: [SPM] No contrast(s) in flexible factorial design
>
>
> Dear Guillaume,
>
>
> Thanks for your help, it's very helpful!
>
>
> I know why I can't do any contrast in flexible factorial design, I
> thought I don't need to input a value for each column.
>
>
> Best regards,
>
> Chih-Hao
>
> ------------------------------------------------------------------------
> *寄件者:* Guillaume Flandin <[log in to unmask]>
> *寄件日期:* 2017年1月11日 下午 10:39:50
> *收件者:* 連 志浩
> *副本:* [log in to unmask]
> *主旨:* Re: [SPM] No contrast(s) in flexible factorial design
>
> Dear Chih-Hao,
>
> Thanks - glad to hear you have more subjects! With 18 subjects in group
> 1 and 8 in group 2, the contrast is:
> [1 0 0 0 0 0 0 0 ones(1,18)/18 zeros(1,8)]
> but you'd be better off doing a one-sample t-test with the 18 images for
> condition 1 of subjects of group 1.
>
> Best regards,
> Guillaume.
>
>
> On 11/01/17 14:00, 連 志浩 wrote:
>> Dear Guillaume,
>>
>>
>> Thanks for your advice!
>>
>>
>> I input more data to run my 2nd-level model, but the same situation
>> happens again.
>>
>>
>> I selected "Specify All" option, and input followed matrix in Factor matrix:
>>
>> [ 1 1 1 1
>> 2 1 1 2
>> 3 1 1 3
>> 4 1 1 4
>> 5 2 1 1
>> 6 2 1 2
>> 7 2 1 3
>> 8 2 1 4
>> ....
>> ......
>> 97 25 2 1
>> 98 25 2 2
>> 99 25 2 3
>> 100 25 2 4
>> 101 26 2 1
>> 102 26 2 2
>> 103 26 2 3
>> 104 26 2 4 ]
>>
>> In Main effects & Interaction option, I created a main effect (1) and a
>> interaction (2 3).
>>
>>
>> Did I do anything wrong?
>>
>>
>> Best regards.
>>
>> Chih-Hao
>>
>>
>> ------------------------------------------------------------------------
>> *寄件者:* Guillaume Flandin <[log in to unmask]>
>> *寄件日期:* 2017年1月11日 下午 08:50:07
>> *收件者:* 連 志浩
>> *副本:* [log in to unmask]
>> *主旨:* Re: [SPM] No contrast(s) in flexible factorial design
>>
>> Dear Chih-Hao,
>>
>> This is to be expected for a model that includes subject effects. The
>> corresponding estimable contrast is [1 0 0 0 0 0 1/3 1/3 1/3 0 0 0] but
>> you are essentially trying to do a one-sample t-test with three subjects
>> so you should acquire data from more subjects before running a second
>> level model.
>>
>> Best regards,
>> Guillaume.
>>
>>
>> On 11/01/17 06:55, 連 志浩 wrote:
>>> Dear experts,
>>>
>>>
>>> I have a problem when I tried to use flexible factorial design.
>>>
>>>
>>> All the bars below the design matrix are gray, and I can't do any contrast.
>>>
>>>
>>> GUI showed "no contrast(s)" when I open SPM contrast manager, and showed
>>> "!invalid contrast" when I try to input any contrast.
>>>
>>>
>>> It's a 2 x 4 flexible factorial design with a Group factor with 2 level
>>> and a Condition factor with 4 level, and I set 3 factors in my model:
>>>
>>>
>>> Factor 1: Subject, Independence: Yes, Variance: Equal
>>>
>>> Factor 2: Group, Independence: Yes, Variance: Unequal
>>>
>>> Factor 3: Condition, Independence: No, Variance: Equal
>>>
>>>
>>> I would appreciate for any help.
>>>
>>>
>>> Thanks for your reading.
>>>
>>>
>>> Best,
>>>
>>> Chih-Hao
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>> --
>> Guillaume Flandin, PhD
>> Wellcome Trust Centre for Neuroimaging
>> University College London
>> 12 Queen Square
>> London WC1N 3BG
>
> --
> Guillaume Flandin, PhD
> Wellcome Trust Centre for Neuroimaging
> University College London
> 12 Queen Square
> London WC1N 3BG
--
Guillaume Flandin, PhD
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
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