Glossary

Goal Attainment Scaling

By Jason Aiginitis19 Oct 2026

Goal attainment scaling (GAS) scores achievement against goal-specific levels agreed before the outcome is assessed. A common format uses 5 levels, from -2 to +2, with 0 representing the expected result at a stated review date. A scale adapted for mentoring is a local progress aid, not automatically a validated clinical instrument.

Why goal attainment scaling matters

Broad goals such as becoming more consistent leave room for the definition of success to shift. Explicit levels make the expectation inspectable before the work begins. Unlike milestone tracking, which records whether named steps happened, GAS describes different degrees of attainment for a particular goal.

Kiresuk and Sherman's original 1968 paper proposed individual goal scales for evaluating mental-health programmes, including standardised aggregate scoring. That clinical origin does not establish reliability or validity for a scale a mentor writes today. A familiar scoring format does not validate a new measure.

How to use goal attainment scaling in practice

Define the goal, observation window, evidence and all attainment levels before assessment. Record the coaching baseline separately; it is not automatically 0, because 0 means the expected follow-up result. Turner-Stokes's practical GAS guide explains this five-level approach in rehabilitation.

Illustrative mentoring adaptation: a mentee wants to establish a weekly campaign-decision review. A review counts only when the mentee examines the agreed report and records a decision, including a reasoned decision to make no change. Count at most 1 qualifying review per week. Baseline: 1 qualifying review in the preceding 4 weeks; assessment: the final 4 weeks of an 8-week engagement.

Score	Predefined attainment level
-2	0 qualifying weekly reviews in the assessment window
-1	1 qualifying weekly review
0	2 qualifying weekly reviews: expected result
+1	3 qualifying weekly reviews
+2	4 qualifying weekly reviews

The scoring rule is: attainment score = the predefined level matching the observed evidence. If 3 qualifying reviews occurred, this example receives +1; the underlying frequency rose from 1 to 3. Keep the observed result beside the score. This locally written scale describes frequency, not the quality of decisions or business impact.

Agree who checks the records and how disagreements will be resolved. Preserve the original scale if priorities change, then date any replacement. Use individual goal records within client progress tracking; the coaching outcome measurement guide explains why observed improvement is not proof of causation.

Common mistakes

Writing the attainment levels after seeing the result, making the target easier retrospectively.
Combining frequency, quality and revenue in one scale so the levels overlap or contradict each other.
Averaging custom scores across clients as if equal numbers meant equally difficult goals.
Presenting an ad-hoc mentoring scale as clinically validated or turning its score into a mental-health assessment.

Frequently Asked Questions

What does 0 mean in goal attainment scaling?

In the common five-level GAS format, 0 means the expected outcome at the agreed assessment date. It does not necessarily mean no progress or the starting point.

Is a custom coaching GAS scale clinically validated?

No. Using GAS labels does not establish a custom scale's reliability, validity or clinical suitability. Evidence from a clinical application cannot simply be transferred to unrelated mentoring goals.

Should a mentor calculate a GAS T-score?

Do not use an aggregate T-score to imply validated measurement of ad-hoc coaching goals. For a practical progress discussion, retain the individual attainment level, its definition and the underlying observation; formal aggregation needs appropriate methodological expertise.