I am not sure what you mean by biological replicate. For me, each individual plat is a biological replicate. So you had 15 bio. reps (= different plants) in each group (15 x 2 groups = 30 er experiment), and you replicated the entire experiment three times (with new, different plants, so these are again all bio. reps). leasecorrect me if I am wrong.

If this is correct, you can simply analyze the data from all 90 plants in one model. There might be some systematic differences between the experiments, which can be accounted for by adding the experiment ID as a random factor.

Hi Doroteja,

Are you sure the 30 plants are one measurements each or did you measure 30 plants individually? In addition, how were the plants grown? All together in blocks?

This is important as what you determine as biological replicates may actually be blocks, which would allow you to use the individual replicates. But with inclusion of your experimental design as random variables in a mixed model or nested anova kind of setup.

Best,

Roel

Roel van Bezouw The plants were grown individually, 1 plant per tube. 30 plants per control group, 30 per treatment group, in total 60 plants in one experiment, such a set up was then repeated thrice. Three experiment were done weeks apart from each other.

Jochen Wilhelm Thank you for your answer. That's what I was thinking too. However as I'm new to this, just wanted to check if my thinking was correct.

Doroteja Vaitiekunaite ;

Indeed, LMM including experiment as a random factor is correct here. Now hope that there is no interaction effect.