Statistical methods	Very good	Adequate	Doubtful	Inadequate
7a. For continuous scores: was an ICC calculated?	ICC calculated; the model or formula was described, and matches the study design and the data	ICC calculated but model or formula was not described or does not optimally match the study design OR Pearson or Spearman correlation coefficient calculated WITH evidence provided that no systematic difference between measurements has occurred	Pearson or Spearman correlation coefficient calculated WITHOUT evidence provided that no systematic difference between measurements has occurred OR WITH evidence provided that systematic difference between measurements has occurred
8a For ordinal scores: was a (weighted) Kappa calculated?	Kappa calculated; the weighting scheme was described, and matches the study design and the data	Kappa calculated, but weighting scheme not described or does not optimally match the study design
9a. For dichotomous/nominal scores: was Kappa calculated for each category against the other categories combined?	Kappa calculated for each category against the other categories combined

Note: Grey shading—these questions were not utilised in this systematic review as all transepidermal water loss (TEWL) devices produce continuous scores.

Abbreviation: ICC, intra‐class correlation coefficient.