What type of validity must Sun Mi establish to differentiate loneliness in her questionnaire?

In the context of Sun Mi's questionnaire focused on loneliness, the emphasis is on discriminating loneliness from other constructs that may be related but distinct, such as social anxiety or depression. Discriminant validity is crucial when researchers want to ensure that their measure is uniquely capturing the concept it aims to assess, rather than being influenced or confounded by other similar constructs.

Establishing discriminant validity involves demonstrating that the questionnaire does not correlate too highly with measures of different but related constructs. This helps validate that the questionnaire is specific to loneliness, providing assurance that the results can be interpreted accurately in relation to that specific emotional state.

While content validity ensures the questionnaire adequately covers the concept of loneliness, and construct validity assesses whether the questionnaire accurately measures the theoretical construct it is intended to represent, discriminant validity focuses specifically on differentiating loneliness from potentially overlapping constructs. Criterion validity, on the other hand, would involve relating the questionnaire's results to an external standard or outcome, rather than differentiating among concepts.