SmartPLS 3.0 and small sample size

Questions about the implementation and application of the PLS-SEM method, that are not related to the usage of the SmartPLS software.
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spangler
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SmartPLS 3.0 and small sample size

Post by spangler »

Hi all,

I am testing a model in SmartPLS 2.0 and SmartPLS 3.0 The model and data are the same; the program are on
different computers. In SmartPLS 3.0 when I create an
interaction term of two variables I get the message that the sample size is too small, due to having more indicators in the
interaction term than number of observations. In SmartPLS 2.0 this is not a problem, the model runs. What is the
difference between the two versions of SmartPLS?. One reason for using PLS is to explore complex models with small sample size. Also, when I reduce the
number of indicators of one of the variables to reduce the number of interaction indicators, the resulting
coefficient in SmartPLS 3.0 is different from that in SmartPLS 2 though the remaining coefficients and R2s in the model
are the same. (I reduced the number of indicators in the SmartPLS 2.0 model also.) Any help
would be greatly appreciated.
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cringle
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Re: SmartPLS 3.0 and small sample size

Post by cringle »

There is no need to take SmartPLS 2 as a reference (it's beta). We fixed some issues in the interaction term computation in SmartPLS 3.2. That's the reason why the results may differ:
https://www.smartpls.com/release_notes

However, basic PLS-SEM results are certainly identical in SmartPLS 2 and SmartPLS 3 since we did not change the basic PLS algorithm.
https://www.smartpls.com/faq/why-do-sma ... lts-differ

So, the difference results from the interaction term computation that we imporved in SmartPLS 3.

What smaple size do you use?

Kind regards,
Christian RIngle
spangler
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Re: SmartPLS 3.0 and small sample size

Post by spangler »

Hello Christian,

Thanks for the quick response. N = 97. There are four predictor LVs in the model, one with
7 indicators, the others have about 30 - 40 indicators each. We need to create interaction terms using the
seven-item LV and each of the others.
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cringle
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Re: SmartPLS 3.0 and small sample size

Post by cringle »

The product indicator approach does not work since you have 7*30 products. This number is larger than your sample size and cannot be estimated. Try the two-stage approach.
spangler
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Re: SmartPLS 3.0 and small sample size

Post by spangler »

Thanks. I experimented some. It seems that eliminating a few indicators from one or the other of the main effects to allow the product method
yields a larger interaction term than using the two-stage approach with all of the initial indicators. Is this correct in general?
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cringle
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Re: SmartPLS 3.0 and small sample size

Post by cringle »

It often looks like this, but the result may not be correct ;) In line with simulation studies and our own experiments, we suggest using the two-stage standatdized options in SmartPLS 3.

Best regards,
CR
spangler
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Re: SmartPLS 3.0 and small sample size

Post by spangler »

ok, thanks for the recommendation.
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