EG
If I claim you’re good at juggling based on how well you describe the process of juggling, the validity of my inference is low.
Whereas if I claim you're good at juggling based on how well you juggle 3 balls for 1 minute, the validity of my inference is much higher.
If I claim you’re good at juggling based on how well you describe the process of juggling, the validity of my inference is low.
Whereas if I claim you're good at juggling based on how well you juggle 3 balls for 1 minute, the validity of my inference is much higher.
Comments
Validity isn't a property of a test itself.
Instead, it relates to the inferences we draw as the result of a test.
If they all answered correctly, I could conclude—with reasonable validity—that they understand osmosis.
But any conclusions I draw about their wider understanding of science would be much less valid.
I could construct a fairly valid assessment of a 6yo’s times-tables understanding by testing them on all their times-tables.
But if I want to gauge the understanding of a 16-year-old, I can't easily test them on everything they should know... this would take days.
Finally, the stakes we attach to any assessment should be in proportion to the validity of our inferences.
Otherwise, it just ain’t fair.