## Indirect adjusted comparisons in BE [General Statistics]

Dear all (and esp. Shuanghe),

I don’t want to hi-jack ElMaestro’s thread about spreadsheets any longer.

Shuanghe and I had an OT-discussion about indirect adjusted comparisons in BE starting here.

I must confess that I don’t get what Luther Gwaza

Sounds great but

@Shuanghe: How did you do it?

I don’t want to hi-jack ElMaestro’s thread about spreadsheets any longer.

Shuanghe and I had an OT-discussion about indirect adjusted comparisons in BE starting here.

I must confess that I don’t get what Luther Gwaza

*et al.*^{1,2}means by his “pragmatic method”:This method does not require the assumption of homogeneity of variances (\(SE_d=SE_{A}^{2}+SE_{B}^{2}\)), since it is unlikely verifiable, between studies with small sample sizes that follow Student’s *t*-test distribution (*t*_{0.9,d.f.}), whose degrees of freedom are approximated for simplicity as if the variances were homogeneous (*n*_{1}+*n*_{2}–2).

Sounds great but

*how*does he pool variances here? If they are weighted by the studies’ sample sizes – which IMHO, is the correct method – we end up in the homoscedastic method, where (in his notation):$$SD_{pooled}^{2}=\frac{(n_1-1)SD_{1}^{2}+(n_2-1)SD_{2}^{2}}{n_1+n_2-2}$$ BTW, is this a typo in the quote? A pooled variance as the sum? I suspect that he simply used the arithmetic mean which would not be correct even for equal samples & variances.@Shuanghe: How did you do it?

- Gwaza L, Gordon J, Welink J, Potthast H, Hansson H, Stahl M, García-Arieta A.
*Statistical approaches to indirectly compare bioequivalence between generics: a comparison of methodologies employing artemether / lumefantrine 20/120 mg tablets as prequalified by WHO.*Eur J Clin Pharmacol. 2012;68(12):1611–8. doi:10.1007/s00228-012-1396-1.

- Gwaza L.
*Adjusted Indirect Treatment Comparisons of Bioequivalence Studies.*PhD Thesis: Utrecht. 2016. free resource.

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Helmut Schütz

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### Complete thread:

- Indirect adjusted comparisons in BEHelmut 2019-07-21 15:20 [General Statistics]
- Pragmatic assumptions mittyri 2019-07-22 01:46
- Indirect adjusted comparisons in BE Shuanghe 2019-07-22 09:53
- Indirect adjusted comparisons in BE nobody 2019-07-22 13:32
- Indirect adjusted comparisons in BE Shuanghe 2019-07-22 15:20

- Indirect adjusted comparisons in BE Helmut 2019-07-22 15:45
- Indirect adjusted comparisons in BE nobody 2019-07-22 18:38

- Indirect adjusted comparisons in BE nobody 2019-07-22 13:32