[throwawaymath]

You really should. If the sample is "all the gas turbines you own" and you disproportionately use Siemens sensors, your turbine failure forecast will (with high likelihood) reduce to a Siemens sensor forecast. This is easily plausible even if your sample's correlation between Siemens sensors and gas turbines is completely superfluous.

[DuskStar]

You can't have a sampling bias when 'sampling' the entire population, because the definition of 'sampling bias' includes 'some members are not included in the sample'.

[throwawaymath]

Precisely, yes. I'm talking about a sample including all representative gas turbine failures, across all sensor vendors.

[TheCoelacanth]

You can't make predictions when sampling the entire population.