HR found that job postings published as short videos received notably more resumes, and the recruiting manager proposed converting all postings to short-video format. To test whether the short-video format itself attracts more applications, what is the next step that should be taken?

Answer: A

• APick two departments with similar job roles, keep the text-and-image format for one and switch to short videos for the other, hold all other conditions constant, and compare the number of resumes received.✓ Correct: This involves changing only the factor in question on a small scale with a control group and fixed other conditions. If the only difference is the posting format and resume counts differ, a causal explanation is supported.
• BRetrieve application data for all postings over the past year and use a model to control for salary, location, and other factors to estimate the effect.✗ Wrong because statistical control cannot replace actual intervention: unobserved differences in historical data (such as job appeal or team reputation) may still affect both the choice of format and application volume, so the estimate remains correlational.
• CFirst interview candidates who applied through short-video postings one by one to find out their true reasons for applying.✗ Wrong because collecting subjective feedback is not the same as testing causality: interviews can only provide clues, and the sample consists entirely of people who already applied, so it cannot answer whether changing the factor changes the outcome.
• DDirectly switch all postings to short-video format for a three-month trial and observe whether the total number of resumes rises noticeably.✗ Wrong because the change lacks a control group: during the three months, conditions such as market trends and the number of positions also change, so even if resume volume rises, it cannot be attributed to the posting format itself.