Apply the course version boundaries in notes.md; HSK tasks are transferable language practice, not a claimed HSK 3.0 mock.
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gre_psychology:mixed-revision:1
A researcher assigns volunteers randomly to two study methods. Identify what random assignment addresses and what volunteer recruitment still limits.
Answer and reasoning
Random assignment reduces systematic confounding between groups. Volunteer recruitment may limit generalisability; assignment is not random sampling.
gre_psychology:mixed-revision:2
A bell repeatedly precedes food and later evokes salivation. Identify the learned cue and distinguish reinforcement of a voluntary action.
Answer and reasoning
The bell becomes a conditioned stimulus in classical conditioning. Operant reinforcement depends on consequences of an action, rather than a predictive cue-food pairing alone.
gre_psychology:mixed-revision:3
A test is stable across administrations but systematically underestimates the target skill. Explain reliability and validity separately.
Answer and reasoning
Stable measurements support test-retest reliability. Systematic underestimation challenges the proposed interpretation; reliability does not establish validity.