Validity and reliability.

The idea

Validity and reliability describe the quality of data collected when preparing for and monitoring training. Validity means the test or measure assesses what it claims to assess: a vertical jump test is valid for explosive leg power but not for aerobic endurance. Reliability means the test produces consistent results when repeated under the same conditions: a stopwatch-timed sprint is reliable if the same protocol, timing method and surface are used each time. A measure can be reliable but not valid, for example a consistently miscalibrated set of scales giving the same wrong mass. A measure can also be valid in principle but unreliable in practice if procedures vary. Together they determine how much confidence a performer or coach can place in data when adjusting a programme.

What earns the marks

• Validity is the extent to which a test or measure assesses what it claims to assess.
• Reliability is the extent to which a test or measure produces consistent results when repeated under the same conditions.
• A valid test must be appropriate to the component being measured, for example a vertical jump test for explosive leg power rather than aerobic endurance.
• Reliability depends on controlling conditions such as protocol, equipment, timing method and environment.
• A measure can be reliable but not valid, for example consistently inaccurate equipment.
• A measure can be valid in principle but unreliable in practice if procedures are not standardised.

Common mistakes and how to put them right

• Treating validity and reliability as the same thing.

  Put it right: Validity concerns whether the right quality is measured, while reliability concerns consistency of results.

• Assuming a reliable test is automatically valid.

  Put it right: A test can give consistent results while measuring the wrong quality.

• Assuming a valid test is automatically reliable.

  Put it right: A test can be appropriate in principle but give inconsistent results if conditions vary.

• Ignoring standardisation when judging reliability.

  Put it right: Reliability depends on controlling protocol, equipment, timing and environment.

Exam tips

• Define both terms precisely before applying them to a sporting example.
• Use a paired example to show the difference, such as a vertical jump test being valid for leg power but unreliable if jump technique is not controlled.
• When evaluating a test, comment on both validity and reliability rather than only one, and link each to the purpose of the monitoring.