What are confidence bands?

Modified on Tue, 20 Aug at 4:38 PM

In some of the reports, there is a confidence band (also known as a confidence interval) displayed on a bar or graph. A confidence band is a range of values in which there is a level of certainty that the true value lies. It is derived from statistical analysis of the standardisation sample.

Below is an example taken from the Individual attainment report.

In this example Abby Dean achieved a standardised score of 107. The black bar which extends either side of 107, from 102 to 110, is the confidence band.

If Abby were to redo the test, under the same test conditions, she may not get the same score twice. However, you can be reasonably certain that she would get a score in the range shown by the confidence band. Many factors can affect how a learner performs on a test, such as if they are feeling tired, distracted, focused, motivated and so on. They may answer a question slightly differently a second time. The confidence interval allows for these differences.

Abby’s score shows that she is working above the national average of the standardisation sample. The confidence band ranges from the scores that are in line with the national average to the higher end of the scores that are above the national average. Abby can best be categorised as working above the national average, however if she has a difficult day, she may fall just below this.

If a learner has a score that is closer to the borderline of a category, the confidence band gives a better indication of how sure you can be of their performance.

For the demo account, the assessments are for example only and have not been trialled and standardised. All standardisation data provided is mocked up and for illustrative purposes only.