Test identification

Name of test Wechsler Individual Achievement Test - Third UK Edition
Previous version(s) WIAT, WIAT-II, WIAT-II UK, WIAT-II UK-T (literacy only), WIAT-III, WIAT-III UK, WIAT-III UK-T (literacy only)
Subjects Literacy, Maths
Summary Comprehensive assessment of reading, language and numerical attainment.

Assessment screening

Subscales 8 composite scores (1) Oral Language, (2) Total Reading, (3) Basic Reading, (4) Reading Comprehension and Fluency, (5) Written Expression, (6) Mathematics, (7) Maths Fluency, (8) Total Achievement.16 subtests; Listening comprehension, Oral expression, Early reading skills, Word reading, Pseudoword decoding, Reading comprehension, Oral reading fluency, Alphabet writing fluency, Spelling, Sentence composition, Essay composition, Maths Problem solving, Numeracy, Maths Fluency - Addition, Subtraction, Multiplication.
Authors David Wechsler
Publisher Pearson Clinical
Test source https://www.pearsonclinical.co.uk/Psychology/ChildCognitionNeuropsychologyandLanguage/ChildAchievementMeasures/wiat-iii/wechsler-individual-achievement-test-third-uk-edition-wiat-iii-uk.aspx
Guidelines available? Yes
Norm-referenced scores. Yes
Age range 4:0 -25;11 Years
Key Stage(s) applicable to KS1, KS2, KS3, KS4, KS5
UK standardisation sample Yes
Publication date 2017
Re-norming date n/a


Validity measures available? Yes
Reliability measures available? Yes
Reason for exclusion from shortlist shortlisted

Evaluation and Appraisal

Are additional versions available? WIAT-IIIUK (reviewed here) is a significant revision of WIAT-IIUK including updated norms, new subtests, revised subtests with new items. Based on WIAT-III (US version)See also WIAT-IIIUK-T.
Can subtests be administered in isolation? Yes(Note that some subtests cover specific age ranges)
Administration group size Individual
Administration duration Dependent on many factors, administration times for each subtest by age and ability is presented on p12 of Examiner's manual.Total achievement composite 30 minutes-60 minutes for younger children, 1.5-2 hours for older children/adults.Few subtests should take >15 minutes to administer.
Description of materials needed to administer test Materials included in the test kit:Examiner's manual (once familiar with procedures, the manual states that the examiner will not need to use the manual during administration),Simulus book,Oral Reading Fluency Booklet,Word card,Pseudoword card,Record form,Response bookletScoring workbook,Audio files (on USB flashdrive).Other recommended materials:Clipboard,Stopwatch/watch with second hand,Audio recorder,Audio player with external speakersBlank paper (blank/lined depending on subtests being administered)Penciles with and without rubbers
Any special testing conditions? Well lit, quiet environment free from disruptions and interruptions.4-8 year olds should not have alphabet displayed in the room.

Response format

Response mode Oral /paper and pencil/manual (physical) operations
What device is required n/a
Queston format. open ended
Progress through questions adaptive

Assessor requirements

Is any prior knowledge/training/profession accreditation required for administration? Yes
Is administration scripted? Yes


Description of materials needed to score test Examiner's manual,Scoring workbook (for alphabet writing fluency, sentence composition and essay composition subtests),UK Scoring and Normative manual OR Qglobal subscription
Types and range of available scores Raw scores on each subtest;Weighted raw scores (corrected for item set) by subtest and composit;Standard score by age (40-160 - available for each subtest, composit and overall achievement, and analyses of differences are provided to allow users to determine whether differences in subscale performance are significant);Percentile Rank (1-99 - available for each subtest, composit and overall achievement);Age equivalent (4;00-25 available for each subtest, composit and overall achievement);Normal curve equivalent (1-99)Stanine (1-9);Cummulative percentages.Skills analyses can be conducted on most subtests.Users are also encouraged to provide behavioural and qualitative observations on the record form to support interpretation.
Score transformation for standard score Age standardised
Age bands used for norming 4;00-13;11 at 4 month intervals,Combined intervals for ages 17-19 and 20-25 (reflecting slower rate of academic change in older agres)
Scoring procedures Using manuals: complex manual scoring – training requiredAnnual subscription to Qglobal: computer scoring with manual entry of responses from paper form/
Automatised norming Computerised/online

Construct Validity

Does it adequately measure literacy, mathematics or science?
Does it reflect the multidimensionality of the subject? Generic literacy and generic maths (with specific subtests)
Construct validity comments (and reference for source) Good detail about face validity for use for diagnostic purposes. Adaptations needed for Anglicisation from WIAT-III described in detail to the examiner's manual and the UK scoring and normative manual. Construct validity is supported by moderate-strong intercorrelations between subtest age-based standard scores (.37-.99), as well as appropriate correlations with previous versions of the WIAT. 79 children aged 6;2-16;10 completed WIAT-IIIUK and WIAT-IIUK with a testing interval of 14-49 days. Correlations were high or moderate for similar subtests (word reading .81; spelling .83) and lower for dissimilar subtests (word reading and numerical operations .28). The US version also shows good evidence of construct validity through correlations and discrepancy analyses with otehr measures (e.g., WPPSI-IV, WAIS-IV) and these findings are likely to transfer to the UK edition. See UK Scoring and Normative manual for further detail. Evidence of contrasted group validity would have further supported diagnostic use, however would not be possible from the standardisation sample due to the nature of exclusionary criteria and stratification in sampling.

Criterion Validity

Does test performance adequately correlate with later, current or past performance?
Summarise available comparisons n/a


Is test performance reliable?
Summarise available comparisons The UK scoring and normative manual indicates good reliability. Good-excellent internal consistency (coefficients .81-.97; SEM 1.5-8.35).(presented by age group and overall for each subtest).95% confidence intervals 3-16; 90% confidence intervals 2-13(presented by age group and subtest).Test-retest reliability and inter-rater reliability are not reported in the UK version of the test. However, other measures of validity are available that were established on the WIAT-III US standaridsation, which are likely to be somewhat transferable, but here we limit to discussion of the UK studies.

Is the norm-derived population appropriate and free from bias?

Is population appropriate and free from bias? Yes
If any biases are noted in sampling, these will be indicated here. Sampling for standardisation is excellent - WIAT-IIIUK standardisation project aimed to provide UK norms based on a census-matched sample of 744 UK children aged 4;0-25;11. Sample was recruited through a range of methods described in detail (see p355 of the UK scoring and normative manual) and stratified by gender, age, parent educational level, race/ethnicity, geographic region. A number of exclusion criteria were included, meanwhile one participant with form diagnosis of learning difficulty and one participant labelled as gifted and tallented were included in each age band. Detailed information about sample demographics compared to census data are provided in the UK scoring and normative manual.


Sources Wechsler, D. (2017). Wechsler Individual Achievement Test - Third UK Edition. Examiner’s Manual. London, UK: Pearson Assessment.Breaux, K. C. (2017). Wechsler Individual Achievement Test - Third Edition. Techinical Manual With Adult Norms. Bloomington, MN, USA: Pearson Clinical Assessment/PsychCorp.Pearson Development Team. (2017). Weschler Individual Achievement Test - Third UK Edition. UK Scoring and Normative Manual. London, UK: Pearson Assessment.