Separate reliability, validity and norms
Course overview · 4 min reading + 12 min practice, estimated
Principles and method
Reliability concerns consistency of measurement under relevant conditions. Validity concerns the evidence supporting an interpretation and use of scores. A consistently measured feature can still be irrelevant to a job. Norms describe the reference group used for comparison; their relevance depends on who was included and when. Scores contain uncertainty and should not be treated as perfectly precise rankings. Ask for technical documentation appropriate to the intended population and language. Do not compare percentile ranks across unrelated instruments as if they were interchangeable units.
Worked example
A candidate’s 70th percentile means their score is above a specified proportion of the reference group under that test’s method. It does not mean they have 70% of the skill or a 70% chance of job success.
Put it into practice
Explain reliability, validity and percentile rank in plain language to a fictional hiring manager.
Use fictional information and keep your work in your own notes.
Compare your approach: self-review guidance
Use one example showing that reliable measurement can still be irrelevant. State the reference group when interpreting a percentile and avoid converting it into a probability of successful performance.
Sources and further reading
Original Academy teaching and fictional examples. These references provide context, not endorsement. Edition 2026.09; updated 2026-09-24.
- CIPD: Selection methods
Professional context for selection methods and their limitations.
- GOV.UK: Discrimination in recruitment
UK legal context. Obtain advice for your jurisdiction and circumstances.