Ability Offset (Months) score type

The Ability Offset (Months) type in Scorelink is the source of much confusion to new users, so this document will clarify what these numbers represent, and how they are calculated. Once understood, the ability offset can be a powerful tool to interpreting and analysing your data effectively.

Age-based Testing

There are several tests (SA Spelling and Waddington to name a couple) that convert a students final raw score into an output value that represents an age, in years and months. These scores only carry meaning when used in comparison with the student’s age on the test date. After all, is a score of 8y 6m good? For a 6-year-old it’s excellent; for a 10-year-old it isn’t. Therefore it’s important we include the student’s chronological age on the test date as a part of our analysis.

The offset type

To combat the challenges listed above we take the data-conversion process one step further, to make your analysis as easy and transparent as possible. Once the student’s score is converted into a spelling- or reading-age we then calculate the student’s chronological age, and deduct it from their test score. This produces what we call an Ability Offset, which represents how many months above (+) or below (-) the student tested at. For example, an offset score of -15 means “15 months below” or “1y 3m below” their chronological age on the test date; conversely, a score of 24 would mean “24 months above” or “2y above”.
Using this offset type to chart progression means we can accurately determine whether a student is actually improving as they age, or if they are slowly slipping behind.

Interpreting the data

Interpretation of the data becomes easier than ever, as teachers no longer have to look up the students age when viewing results: this information is all encapsulated in the offset score.
Analysing growth between two points in time also becomes more straightforward as the student’s age is already taken into consideration. This means we can graph the offset values without worrying about how much time has passed in-between.

Benchmarking with offsets

When it comes to benchmarking, the offset type makes things really simple. The numbers you set will reflect how far above or below their age the student is, so one benchmark will usually do for all students. Of course you can still set multiple benchmarks if you want. eg. A Year 3 student 6 months ahead of their chronological age is comparable to a Year 7 student 6 months ahead, which means that we can apply the same benchmark for all students.
When you look at the range values for offset types you will see the minimum accepted value is -192 and the maximum is 192; these represent -16y 0m to +16y 0m. The reason for this is because Scorelink needs min/max values to validate your data, so we set them to the most extreme conceivable values we could imagine: that way there is no chance of a student scoring outside the bounds (even if they do really really really well!).

Tagged: Deep-dive