Tests of Dyslexia (TOD)


Browse subjects

  • Suitability
  • Administration
  • Scoring
  • Psychometric properties
  • Structure of the TOD
  • Qualification requirements
  • Further information
  • References


Do all the subtests in the TOD-Comprehensive have an age ceiling of 89.11?

Yes, all TOD-Comprehensive tests go through 89 years, 11 months.


Is there a digital version?

The TOD manual, norms, administration booklet, intervention guide, and TOD-E and TOD-C easels are available in pdf digital format. Examiners can use the TOD-E and TOD-C pdf easels for remote administration, but paper materials, record forms, and response booklets are still required. Free online scoring for TOD-S, TOD-C, and TOD-E is available on the WPS Online Evaluation System (platform.wpspublish.com). The TOD-Screener is available as a paper kit or an online kit with full online administration capabilities, without the use of paper materials. TOD Rating Scales are administered and scored online only. 


Do I need to purchase the TOD-Screener Print Kit in addition to the TOD-Combination, TOD-Early or TOD-Comprehensive?

No. The print screening materials are included in the TOD-Combination Kit, TOD-Early Kit and TOD-Comprehensive Kit.


How do I access the TOD rating scales? 

The rating scales included in the TOD-C, TOD-E, and TOD Combination kits are only available on the WPS Online Evaluation System™ (OES) at platform.wpspublish.com. Once you use the activation code on the OES, you can print out any of the Parent, Teacher, or Self-Rating Forms at no extra cost and as many times as you want if you prefer to administer any forms on paper. However, you still have to score the response forms online, which gives you access to beneficial reporting options.


How do I score the TOD?

The TOD-S can be administered digitally on the WPS OES and scored automatically or can be administered on paper. The TOD-C and TOD-E can only be administered on paper (although pdf easels are available for remote/digital administration, responses are recorded/scored on a paper record form). When administered on paper, the TOD-S, TOD-C, and TOD-E can be hand-scored or scored on OES for free. This free online scoring and reporting provides a convenient alternative to hand-scoring as well as an interpretive score report and access to a customisable intervention report.

Psychometric properties

What is the reliability/validity of the TOD?

The answer to this question is complicated and requires some context. Reliability and validity evidence occurs over time and from multiple studies and methodologies. It cannot be defined by single scores. Expert recommendations for interpreting reliability and validity estimates are produced by statistical equations.  

Reliability estimates are assumed to reflect the percentage of systematic variance in a test (vs. error) and can be calculated using statistical equations. The two most common reliability formulae are Cronbach’s Alpha and Spearman-Brown. Both yield coefficients designed to estimate the magnitude of the linear relationship between two variables, perhaps two versions of the same test. The most common correlational statistics assess relationships between either two interval-level variables (i.e., the Pearson Product Moment Correlation Coefficient) or two ordinal variables (i.e., Spearman’s Rho). Authors of tests and measurement texts (e.g., Sattler, 2018) provide criteria for interpreting these reliability coefficients (after Murphy & Davidshofer, 2005).  

Values above .90 are considered high/excellent; .80 to .89, moderately high or good; .70 to .79, moderate or fair; .60 to .69 low or poor; and .00 to .59, very low. Reliability coefficients set the limits on validity; for example, the square root of a reliability coefficient of a test defines the maximum predictive validity of that instrument. 

Validity is traditionally defined as the extent to which a test does what it was designed to do and, like reliability, is typically operationalised using correlation coefficients. Understanding the conceptual nature of “validity” is more complicated than reliability. Tests are valid for particular purposes. For example, validity coefficients address the extent to which a test assesses the construct it was created to address.  

Thus, construct validity is determined in part by how strong the correlation coefficient is between the test in question, say a newly developed test, and an established instrument that measures similar skills. In addition, validity data can inform prediction, i.e., how well a test predicts some criterion of interest. As an example, intelligence tests are often used to predict academic achievement. Across many studies reported in test manuals and in the general literature, these validity coefficients typically range from about .40 to .70, indicating that the percentage of the variance accounted for in achievement by intelligence ranges from about 16% to 49%.  

Reliabilities for the TOD tests and composites are typically good (i.e., greater than .80), as reported in the TOD Manual. Similarly, validity estimates are good also. For example, the TOD-C Dyslexia Diagnostic Index is a strong predictor of the probability of dyslexia.  

In summary, data generally support the reliability of the TOD indexes, composites, and tests and the validity of these scores for their intended purposes. Consequently, examiners can have confidence in the TOD scores.  


Is a certain group contained in the standardisation or clinical sample?

The TOD has U.S. norms. 2,518 individuals aged 5 to 89 participated in the standardisation and validation studies. The TOD normative samples are TOD-C child (n = 1,401); TOD-C adult (n = 342); and TOD-E (n = 347). The TOD-S was taken by individuals in each of the three samples and serves as the basis for the TOD-S standardization. Each sample closely matches U.S. Census data based on gender, race/ethnicity, parents’ educational level, and geographic region. The remaining individuals made up the clinical validation samples and had a reading disability and/or other clinical diagnosis.

Structure of the TOD

Does the TOD provides information on underlying visual and verbal ability (as opposed to attainment), as the WRIT does?

The TOD is far more comprehensive of an assessment than the WRIT and designed to capture most of the important abilities relevant to dyslexia. In comparison to the Verbal Scale on the WRIT, there are two vocabulary measures on the TOD. In comparison to the Visual Scale on the WRIT, there are two fluid reasoning tests on the TOD, so similar constructs are being measured by both tests. The authors of the TOD do not really distinguish between the hypothetical concepts of ability and attainment as both are influenced by each other. Abilities can change as one attains more knowledge. The reasoning tests may, however, be viewed as a measure of reasoning ability, whereas the vocabulary tests are more of a reflection of attainment and educational experience. The TOD was primarily designed to measure the linguistic risk factors and the reading and spelling abilities that are most impacted by dyslexia.

Qualification requirements

Who can use the TOD?

  • The components of the TOD can be used by a variety of clinicians and educators. For example, a classroom teacher may administer the TOD-Screener and complete the Teacher Rating Scale.
  • Reading specialists, specialist teaching assessors, psychologists, and speech and language therapists are best suited to administer the TOD-Early or the TOD-Comprehensive due to their advanced coursework and experience with standardised tests.
  • Teachers that are trained to administer the test and are supervised by professionals who have advanced training with standardised assessments may also administer the TOD-E or TOD-C.
  • Interpretating test results requires a higher level of skill. For that reason, while a broader range of individuals can administer the test, interpretating results requires a knowledge of dyslexia and formal training in test administration, scoring, and interpretation.

Examiners should use only those tests for which they have the appropriate training and expertise. See Hogrefe's guidelines here or contact us to discuss. 

Further information

Where can I find out more about the TOD?

You can find information on the TOD, plus extra resources and free samples to download here. If you have any questions, feel free to contact us at customersupport@hogrefe.co.uk



Murphy, K. R., & Davidshofer, C. O. (2005). Psychological testing: Principles and applications (6th ed). Pearson Education. 

Sattler, J. M. (2018). Assessment of children: Cognitive foundations and applications (6th ed). Jerome M. Sattler Publisher.  

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