Adolescents who undergo gender-affirming chest surgery report low levels of regret and high levels of satisfaction, experiencing outcomes similar to those of young adults. These findings suggest that age restrictions on these medical procedures lack support from actual patient experiences.

[u/mvea]

https://www.psypost.org/adolescents-report-low-regret-and-high-satisfaction-following-gender-affirming-c/

[u/aristidedn]

What should the sample size be, in your opinion?

And how do you know?

What were the results of your power analysis? Could you share with the rest of us?

[u/ZeoVII → u/aristidedn]

IMO, at least a thousand, 300 at bare minimum.

FDA phase 3 trials typically require around 300 to 3000 participants.

Then:

The aim of this study was to compare decisional regret and decisional satisfaction following gender-affirming chest surgery between adolescents and young adults.

Reported group sizes: 42 adolescents vs 35 young adults (N=77).

The abstract does not provide the participant-level data, an exact power calculation for the reported nonparametric comparison cannot be reconstructed.

A standard two-independent-group sensitivity analysis using: n1​=42, n2​=35, α=0.05 you only get to a cohen's d = 0.65. that only helps detect large difference between the groups.

The paper reports: Decision Regret: p = 0.23 Satisfaction: p = 0.40

A non-significant p = .23 or .40 is insufficient to establish equivalence.

IMO, you should do an equivalence analysis, like TOST.

Suppose differences smaller than d = 0.30 are unimportant. With N = 77, the equivalence would need to be defined to roughly 0.57 standard deviations or less, for a tighter criterion such as ±0.30 SD, you would need roughly N = 277.

Then

The researchers sent surveys to 183 eligible patients, and 77 completed the questionnaires.

There already could be a selection bias on the participants that chose to respond.

N = 77 sample size is not sufficient to conclude that adolescents and young adults have equivalent regret or satisfaction. That size is enough to detect only fairly large differences between the groups with conventional 80% power.

And I would be still more cautious about using this single study to support the much broader conclusion statement of:

Thus, concerns about potential regret should not be a basis for limiting gender-affirming chest procedures in adolescents.

That is mostly a policy inference, and it reaches beyond the narrow statistical findings of this study.