Table 2 Studies internal validity critical appraisal tool

Confounding factors

Are there potential confounding factors influencing the exposure and/or outcome? (e.g. different ecosystems between sites, additional uncontrolled exposures such as light, chemical or noise pollution)

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Post-exposure selection

Are exposure and comparator groups randomly or systematically selected and exchangeability can be assumed after the exposure?

Yes or Seemingly yes

No or Seemingly no

Unknown or Unclear

Attrition

Were there any differences in missing data between exposure and comparator groups during the study or the analysis?

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Misclassified comparison (only for observational studies)

Are exposure and comparator groups sufficiently well defined?

Yes or Seemingly yes

No or Seemingly no

Unknown or Unclear

Performance (only for experimental studies)

Was the exposure altered during the experiment and thus differed between exposure and comparator groups?

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Detection

Are they differences in how outcomes were measured between exposure and comparator groups?

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Outcome reporting

Are reported findings selectively disclosed?

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Outcome assessment

Were assumptions for the applied statistical analyses violated? (e.g. normality, homoscedasticity)

No or Seemingly no

Yes or Seemingly yes

Unknown or Unclear

Exposure

Are real (not simulated) photovoltaic or solar thermal panels used?

Yes or Seemingly yes

No or Seemingly no

Unknown or Unclear