Competency-Based Interview Questions: A Hiring Guide

Most hiring mistakes happen in the scoring, not the asking. Interviewers often use sound competency-based interview questions, then judge the answers on fluency and confidence. This guide covers why structure predicts performance, the two question types, example questions for six leadership competencies, how to score answers, and the errors that undo a good interview.

What are competency-based interview questions?

They are questions written to collect evidence of one job-relevant competency, asked in the same way of every candidate and scored against the same standard. The US Office of Personnel Management describes the structured interview as a method that measures job-related competencies by asking systematically about a candidate’s behaviour in past experiences and in hypothetical situations, with one questioning and scoring process for all candidates [Source: US Office of Personnel Management].

In OPM’s model, experts write the questions from the role’s competencies, every candidate hears them in the same order, a trained panel takes detailed notes, and every answer is rated on one scale. Most interviews assess four to six competencies.

A question that cannot be traced to a named, agreed competency is conversation rather than assessment.

Why do structured interviews predict job performance better?

Because structure removes much of the noise that unstructured conversations let in. In a large 2022 re-analysis of selection research, structured interviews emerged as the top-ranked selection procedure [Source: Sackett and colleagues 2022].

Practitioners long relied on Schmidt and Hunter’s 1998 validity estimates. Sackett, Zhang, Berry and Lievens argued those figures were inflated by over-correction for range restriction, and re-estimated them. Most of the leading procedures kept their rank but lost .10 to .20 points of validity. Structured interviews lost .09 and moved to first place, while unstructured interviews fell by half.

Operational validity estimates (correlation with job performance), from Table 3 of Sackett and colleagues 2022.

The authors drew a pointed conclusion: “one might propose structured interviews as the focal predictor against which others are evaluated” [Source: Sackett and colleagues 2022]. A HumRRO summary for SIOP adds a caution: structured interview validities are somewhat variable [Source: SIOP, The Industrial-Organizational Psychologist]. A loosely run interview with a competency label on it should not be expected to match the average.

What is the difference between behavioural and situational questions?

Behavioural questions ask what a candidate has done; situational questions ask what they would do. OPM explains that behavioural questions rest on the premise that past behaviour in similar circumstances best predicts future behaviour, while situational questions rest on the premise that intentions are closely tied to actual behaviour [Source: US Office of Personnel Management].

Both formats work. OPM notes that behavioural description interviews have shown higher validity where the work is highly complex, citing professional and managerial jobs [Source: US Office of Personnel Management].

STAR is the backbone of the behavioural format: every answer should cover the situation or task, the action, and the result.

What are good example competency-based interview questions for leaders?

Good questions name one competency, ask for one specific event, and invite a measurable result. OPM recommends open-ended wording with superlatives such as most, last or worst, which helps anchor an answer to one specific event rather than a general habit [Source: US Office of Personnel Management].

The questions below are illustrative examples written for this guide. Adapt them to your own competency definitions and role level before use.

Plan probes in advance. OPM advises clarifying when candidates say “we did”, and never using leading probes.

How do you score answers with behaviourally anchored rating scales?

Score each answer against written examples of what weak, sound and strong evidence looks like for that competency. OPM recommends one scale of three to seven levels for every competency, with at least three labelled, and asks subject matter experts to agree representative example responses for each level [Source: US Office of Personnel Management].

An illustrative anchor set for “developing others” might read:

• 1, little evidence: describes telling people what to do; no example of growing someone’s capability.
• 3, sound evidence: one clear example of delegating stretch work with some support, and a modest result.
• 5, strong evidence: a specific example of matching stretch to readiness, adjusting support over time, and a visible change in the other person’s capability.

Interviewers should rate independently, question by question, before any group discussion. The CIPD gives the same advice and describes structured interviews as an effective way to minimise bias [Source: CIPD]. Where ratings differ, the panel reaches consensus using notes, not impressions.

What mistakes do interviewers make with competency-based questions?

Most mistakes are judgement errors rather than question errors. OPM’s list of things to avoid includes relying on first impressions, focusing on superficial factors, candidate-order effects, the “similar to me” effect, the halo effect, leniency or strictness, and central tendency [Source: US Office of Personnel Management].

Three practical failures recur:

1. Accepting “we”. A team result is not evidence of the candidate’s own action.
2. Taking a hypothetical answer to a behavioural question. “I would…” is not “I did…”. Ask for a real example or score the gap.
3. Rewarding polish. Fluent, confident delivery is not the competency. A strong executive presence can make thin evidence sound complete.

Structure also protects fairness. OPM reports that interviews with more structure show higher validity, rater reliability and agreement, and less adverse impact [Source: US Office of Personnel Management].

When should you combine interviews with psychometrics or an assessment centre?

Add other methods when the decision is high-stakes, when the candidate has little relevant track record, or when you need evidence of potential rather than past performance. The CIPD advises using several methods for fair selection, and warns that psychometric results should never be the sole basis for a decision [Source: CIPD].

Decision table: when the interview needs company. Validity figure from Sackett and colleagues 2022.

Our guides to psychometric assessment in hiring and assessment and development centres cover each method.

How Phi Management helps organisations interview well

Phi Management runs a one-day structured interviewing programme for managers at all levels, HR professionals and talent managers. It covers the STAR technique, building a question bank, handling vague answers and impression management, and rating frameworks that reduce unconscious bias.

For panels that assess in centres, the two-day Assessor Skills Certification teaches the ORCE model of observing, recording, categorising and evaluating behaviour, plus calibration and reporting. Both sit within Phi’s wider certification programmes.

Where an interview is one input among several, Phi designs assessment and development centres that combine competency-based interviews with role plays, case studies, an e-tray and psychometrics, observed by several assessors. Phi draws on its accreditation across a range of psychometric tools, including Hogan, Saville Wave and the NEO-PI-R. For development rather than selection, 360Quest feedback adds the view of colleagues. Read more about who we are.

Frequently asked questions

How many competency-based interview questions should one interview include? Fewer than most hiring managers expect. OPM suggests most structured interviews assess four to six competencies, so plan one main question per competency, a second if time allows, and a short list of agreed probes for each. Leave room for introductions, candidate questions and note-taking. Asking more questions rarely adds evidence. It mainly reduces the time available to probe each answer properly, which is where the useful detail about the candidate’s own actions and results tends to come out.

Can candidates rehearse their answers? Yes, and many do. Preparation is not a problem in itself, because a candidate still has to recall a real event. The risk is a polished story that hides a thin contribution. Planned probes deal with this: ask who else was involved, what the candidate personally did, what they would do differently, and how they know the result happened. Borrowed or inflated stories rarely survive three specific follow-up questions. Scoring against written anchors, rather than overall impression, also stops a smooth delivery from carrying a weak example.

Are situational questions fair to internal candidates? They are often fairer than behavioural questions for people stepping into their first leadership role. A strong individual contributor may have no past example of managing a team, so a behavioural question about it tests their history rather than their potential. A situational question lets them show judgement and priorities instead. Use the same scenarios and the same anchors for every candidate, internal or external. For promotion decisions with real stakes, add a simulation or an assessment centre so that intentions are tested against observed behaviour.

The bottom line

Competency-based interview questions work when the whole method is structured: questions tied to named competencies, the same questions for every candidate, planned probes and scores anchored in observable behaviour. Get the scoring right and the interview becomes one of the strongest predictors available. To build that capability in your managers and HR team, talk to an expert at Phi Management.