# [MORPHMET] number of landmarks and sample size

```Hello everyone,

I am new in the field of geometric morphometrics and have a question for my
bachelor thesis.

I am not sure how many landmarks I should use at most in regard to the sample
size. I have a sample of about 22 individuals per population or maybe a bit
less (using sternum and epigyne of spiders) with 5 populations.
I have read a paper in which they use 18 landmarks with an even lower sample
size (3 populations with 20 individuals, 1 with 10). But I have also heard that
I should use twice as much individuals per population as land marks... ```
```
Maybe there is some mathematical formula for it to know if it would be
statistically significant? Could you recommend some paper?

Because of the symmetry of the epigyne I am now thinking of using just one half
of it for setting landmarks (so I get 5 instead of 9 landmarks). For the
sternum I thought about 7 or 9 landmarks, so at most I would also get 18
landmarks like in the paper.

I would also like to use two type specimens in the analysis, but I have just
this one individual per population... would it be totally nonesens in a
statistical point of view?

Thanks very much for your help!

Best regards
Lea

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