Hello,
Covid19 is a hot topic, there are many papers published, and many of them with contradicting results. I’d like to know how you would judge the results from this current study (preprint) from one of Germany’s most famous virologists: http://bit.ly/SARS2load
The study investigates viral load for people infected with Covid19. Assumption: higher viral load is strongly associated with higher probability of being infectious. Background: School opening and the question, whether kids may increase the pandemic spread or not. Methods: DV is viral load, IV is age category (e.g. Kindergarten, grade school, uni, adult). Results: no significant differences between kids and adults. Conclusion: Kids may spread Covid19 to the same extent as adults do, thus school opening might increase pandemic spread.
I don’t want to start a discussion about pros and cons of school opening. I have four questions/concerns:

I was wondering, whether the very different sample sizes per category (e.g. n=16 for grade school compared to n = 2071 for people aged > 45), and the KruskalWallis test, can give “robust” results.
Edit: The pairwise comparisons are based on three different approaches, Tukey’s HSD (probably with 1wayanova as input?), tTest (Bonferroni adjusted) and Dunn’s Test for pairwise comparisons. But the point is the same: very different N’s per group. 
The absence of “statistical evidence” was interpreted as “there is no difference” (i.e. accepting H0, which is actually not possible in NHST, only in Bayesian framework?)

Which viral load is actually infectious?

Isn’t the “majority” of viral loads for kids and children rather below the average, while for adults etc. it looks rather uniform distributed, implying that kids are indeed less infectious (though this assumption of course is biased due to small N in groups as well…)
Any comments are welcome.
P.S.: The author of the study also linked to a study (https://science.sciencemag.org/content/early/2020/04/28/science.abb8001) that concluded that kids are only about 1/3 as infectious as adults. That’s a good thing that people are not afraid promoting “counterpartresults”.