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State-Trait Anxiety Inventory (Form Y):
Scoring and Interpretation
The State-Trait Anxiety Inventory (STAI) is a 40-item self-report measure that scores anxiety felt right now (state) and anxiety felt in general (trait) on two separate 20-item scales, each ranging from 20 to 80 (Spielberger et al., 1983). Adult Form Y is the focus of STAI scoring here: the ten state and nine trait reversals, why the two scales stay separate, syntax for SPSS and R, reliability generalization evidence and a methods paragraph reporting both scales.
What the STAI Measures
The STAI separates two things that a single anxiety score would blur: a transient emotional state tied to the present situation, and a relatively stable tendency to experience anxiety across situations. In adult Form Y each of these has its own 20-item scale, so a study can follow a change in immediate state without claiming that the underlying disposition has changed (Spielberger et al., 1983).
The inventory is common in experimental psychology, perioperative research and treatment-outcome studies. Barnes, Harp and Jung (2002) synthesized reliability evidence across published uses and described acceptable coefficients overall, with variation by form, population and measurement occasion. Which form your participants completed therefore matters as much as how you add up the answers.
Structure of the STAI
- State anxiety (Y-1): items 1 to 20, a four-level intensity rating of how the respondent feels at this moment.
- Trait anxiety (Y-2): items 21 to 40, a four-level frequency rating of how the respondent generally feels.
- Scoring: both scales are scored from 1 to 4 after the form-specific item keys are applied.
- Reverse-keyed state items (Form Y): 1, 2, 5, 8, 10, 11, 15, 16, 19 and 20.
- Reverse-keyed trait items (Form Y): 21, 23, 26, 27, 30, 33, 34, 36 and 39.
- Total: none. A 40-item diagnostic total is not part of the conventional scoring.
- Short form: a six-item state version exists (Marteau & Bekker, 1992) and is scored differently from the 40-item Form Y.
The instrument itself is available from Mind Garden.
How to Score the STAI
- Confirm that the administered instrument is adult Form Y and that stai1 to stai40 hold raw responses coded 1 to 4, not item severity values that were already reversed.
- For Form Y only, reverse the state and trait items listed above as 5 minus the response. Every other item keeps its direct value.
- Sum the keyed items 1 to 20 to obtain stai_state and the keyed items 21 to 40 to obtain stai_trait, each ranging from 20 to 80. Keep the two scores apart.
- Handle missing responses by a stated rule. The Form Y manual allows prorating when one or two items on a scale are omitted (the mean of the answered items multiplied by 20 and rounded) and treats a scale as questionable when three or more are omitted. The code below requires all 20 responses on each scale; add prorating if your protocol follows the manual. Form X uses a different key.
* Illustrative syntax: variables must already be valid item scores (1 to 4).
COMPUTE stai1_r = 5 - stai1.
COMPUTE stai2_r = 5 - stai2.
COMPUTE stai5_r = 5 - stai5.
COMPUTE stai8_r = 5 - stai8.
COMPUTE stai10_r = 5 - stai10.
COMPUTE stai11_r = 5 - stai11.
COMPUTE stai15_r = 5 - stai15.
COMPUTE stai16_r = 5 - stai16.
COMPUTE stai19_r = 5 - stai19.
COMPUTE stai20_r = 5 - stai20.
COMPUTE stai21_r = 5 - stai21.
COMPUTE stai23_r = 5 - stai23.
COMPUTE stai26_r = 5 - stai26.
COMPUTE stai27_r = 5 - stai27.
COMPUTE stai30_r = 5 - stai30.
COMPUTE stai33_r = 5 - stai33.
COMPUTE stai34_r = 5 - stai34.
COMPUTE stai36_r = 5 - stai36.
COMPUTE stai39_r = 5 - stai39.
COMPUTE stai_state = SUM.20(stai1_r, stai2_r, stai3, stai4, stai5_r, stai6, stai7, stai8_r, stai9, stai10_r, stai11_r, stai12, stai13, stai14, stai15_r, stai16_r, stai17, stai18, stai19_r, stai20_r).
COMPUTE stai_trait = SUM.20(stai21_r, stai22, stai23_r, stai24, stai25, stai26_r, stai27_r, stai28, stai29, stai30_r, stai31, stai32, stai33_r, stai34_r, stai35, stai36_r, stai37, stai38, stai39_r, stai40).
EXECUTE.# data: one row per respondent; items stai1 to stai40 coded 1 to 4.
data$stai1_r <- 5 - data$stai1
data$stai2_r <- 5 - data$stai2
data$stai5_r <- 5 - data$stai5
data$stai8_r <- 5 - data$stai8
data$stai10_r <- 5 - data$stai10
data$stai11_r <- 5 - data$stai11
data$stai15_r <- 5 - data$stai15
data$stai16_r <- 5 - data$stai16
data$stai19_r <- 5 - data$stai19
data$stai20_r <- 5 - data$stai20
data$stai21_r <- 5 - data$stai21
data$stai23_r <- 5 - data$stai23
data$stai26_r <- 5 - data$stai26
data$stai27_r <- 5 - data$stai27
data$stai30_r <- 5 - data$stai30
data$stai33_r <- 5 - data$stai33
data$stai34_r <- 5 - data$stai34
data$stai36_r <- 5 - data$stai36
data$stai39_r <- 5 - data$stai39
data$stai_state <- rowSums(data[c("stai1_r", "stai2_r", "stai3", "stai4", "stai5_r", "stai6", "stai7", "stai8_r", "stai9", "stai10_r", "stai11_r", "stai12", "stai13", "stai14", "stai15_r", "stai16_r", "stai17", "stai18", "stai19_r", "stai20_r")], na.rm = FALSE)
data$stai_trait <- rowSums(data[c("stai21_r", "stai22", "stai23_r", "stai24", "stai25", "stai26_r", "stai27_r", "stai28", "stai29", "stai30_r", "stai31", "stai32", "stai33_r", "stai34_r", "stai35", "stai36_r", "stai37", "stai38", "stai39_r", "stai40")], na.rm = FALSE)Interpreting STAI Scores
| Score band | Interpretation |
|---|---|
| 20 to 80, State | Higher = greater current (state) anxiety |
| 20 to 80, Trait | Higher = greater general disposition to anxiety |
| Universal clinical cut-off | None established for both scales and all populations |
Source: Spielberger et al. (1983) manual; Barnes et al. (2002).
The two scores share a numeric range but not a meaning, since one describes the moment and the other the person’s usual experience. Raw totals can be set against normative distributions published for the same form and a comparable population. No single cut-off separates an anxiety disorder from its absence across adult groups, so a score is a position on a continuum rather than a diagnostic label.
State scores move with the assessment context, which is an intended property of the scale and not by itself a sign of poor reliability. Item order and the reverse key differ between STAI forms and abridged versions, so check the code against the questionnaire your participants actually completed.
Psychometric Properties
| Property | Published finding | Source |
|---|---|---|
| Internal consistency | Average coefficients acceptable across studies, but varied by sample and form | Barnes et al. (2002) |
| Test-retest | Reliability varies; lower stability for state than trait is expected because states change | Barnes et al. (2002) |
| Validity evidence | State-versus-trait distinction and established usage in experimental research | Spielberger et al. (1983) |
| Factor structure | State and trait are treated as distinct constructs; item wording may influence factor solutions | Spielberger et al. (1983) |
| Short forms | Six-item state short form described by Marteau and Bekker (1992); its scoring differs from the 40-item Y form | Marteau & Bekker (1992) |
These are source-specific results and cannot be assumed to hold as reliability or accuracy estimates in a new sample.
Using the STAI in a Study
Pick the scale that matches the question: the state scale for immediate effects of an intervention or situation, the trait scale for a relatively stable predictor or a stratifying variable. A before-and-after state comparison in one group can be reported with a Paired Samples t-Test as a mean change with its 95% confidence interval, while several measurement occasions call for Repeated Measures ANOVA or a mixed model. A short-term change in state is not evidence of change in the trait.
Report internal consistency separately for the state and trait scales, together with their score distributions, and run each alpha through Reliability Analysis (Cronbach’s Alpha). In perioperative and treatment-outcome work, where the STAI is often a secondary outcome, the analysis should follow the prespecified plan, as described for Clinical Trials. If you compare demographic groups, discuss which norms apply and whether the scale functions equivalently across them. Plan the sample size around the intended comparisons and the correlation between repeated measures.
Related field: Experimental Psychology
Reporting the STAI
Anxiety was assessed with the State-Trait Anxiety Inventory, adult Form Y (STAI; Spielberger et al., 1983). After form-specific reverse scoring, separate 20-item State and Trait scores were computed (each ranging from 20 to 80), with higher scores indicating greater state or trait anxiety. Cronbach’s alpha in this sample was [αstate = XX] for the State scale and [αtrait = XX] for the Trait scale.
References
Barnes, L. L. B., Harp, D., & Jung, W. S. (2002). Reliability generalization of scores on the Spielberger State-Trait Anxiety Inventory. Educational and Psychological Measurement, 62(4), 603-618. https://doi.org/10.1177/0013164402062004005
Marteau, T. M., & Bekker, H. (1992). The development of a six-item short-form of the state scale of the Spielberger State-Trait Anxiety Inventory (STAI). British Journal of Clinical Psychology, 31(3), 301-306. https://doi.org/10.1111/j.2044-8260.1992.tb00997.x
Mind Garden. (n.d.). Manual: State-Trait Anxiety Inventory for Adults. https://www.mindgarden.com/state-trait-anxiety-inventory-for-adults/29-staiad-manual.html
Spielberger, C. D., Gorsuch, R. L., Lushene, R., Vagg, P. R., & Jacobs, G. A. (1983). Manual for the State-Trait Anxiety Inventory (Form Y). Consulting Psychologists Press.
Frequently Asked Questions
What separates state anxiety from trait anxiety on the STAI?
State anxiety describes how a person feels at the time of completion, while trait anxiety describes how they generally feel across situations. They are scored from separate sets of 20 items and answer different research questions.
Should the state and trait scores be added together?
No. Report them separately, each from 20 to 80. A sum would mix a momentary state with a stable disposition and has no validated meaning.
Which STAI items are reverse scored?
The Form Y keys are listed in the structure and scoring sections, with ten state items and nine trait items reversed. Match them to the exact form administered, because other forms and abridged versions use a different key.
Does the STAI have a single clinical threshold?
No threshold is valid for both scales and every population. Identify population-specific references for the form you used and report the continuous scores alongside any categorization.
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