Product Details > Overview | Validity | Reliability | Discrepancies



The Woodcock-Johnson III NU contains two distinct, co-normed batteries: the WJ III NU Tests of Achievement and the WJ III NU Tests of Cognitive Abilities. Both batteries are appropriate for ages 2 to 90+, and together provide a comprehensive system for measuring general intellectual ability (g), specific cognitive abilities, scholastic aptitude, oral language, and achievement.

While tests are the basic administration components of the WJ III NU, test interpretation is based primarily on clusters of tests. Cluster interpretation results in higher validity because scores are based on a broad, multifaceted picture of each ability instead of on a single, narrow ability.

Professionals use the WJ III NU to:



Two important aspects of a test’s validity are: 1) how closely its norming sample represents the population to which the test results will be compared, and 2) how carefully the data were gathered from that sample. The original WJ III sample was selected to represent, within practical limits, the U.S. population from ages 24 months to 90+ years. Normative data for the test were gathered from more than 8,800 subjects in more than 100 geographically diverse communities in the United States. Individuals were randomly selected within a stratified sampling design that controlled for 10 specific community and individual variables and 13 socio-economic status variables. The sample consisted of 1,143 preschool subjects; 4,784 kindergarten through twelfth-grade subjects; 1,165 college and university subjects; and 1,843 adult subjects.

The WJ III NU uses continuous-year norms to yield normative data at 10 points in each grade. It provides age-based norms by month from ages 24 months to 90+ years. And it provides grade-based norms for kindergarten through 12th grade, 2-year college, and 4-year college, including graduate school.

The WJ III NU is a highly accurate and valid diagnostic system because the two batteries were co-normed and based on a single sample. When tests are co-normed, examiners obtain actual discrepancies and avoid errors typically associated with estimated discrepancies.



Most of the WJ III NU tests show strong reliabilities of .80 or higher; several are .90 or higher. The WJ III NU interpretive plan is based on cluster interpretation. The WJ III NU clusters show strong reliabilities, most at .90 or higher.


The WJ III NU is especially useful for identifying and documenting ability/achievement discrepancies and intra-ability variations. The ability/achievement discrepancy is the most commonly used method of evaluating an individual's eligibility for special programs. Professionals can obtain ability/achievement discrepancies by administering both the Cognitive and the Achievement batteries. The WJ III NU provides three types of ability/achievement discrepancies - general intellectual ability to achievement, predicted achievement to achievement, and oral language to achievement.

The oral language to achievement discrepancy is a new measure offered only in the WJ III NU. For the first time, professionals can calculate an ability/achievement discrepancy using only the achievement battery. The Oral Language Extended cluster, which used to be in the cognitive battery, can now be used as the "ability" score and compared with a subject's achievement score. This measure is particularly useful for reading and other oral language professionals. The WJ III NU also provides intra-ability variations, which include intra-achievement variations, intra-cognitive variations, and intra-individual variations. Information gathered from intra-ability variations helps professionals to determine an individual's strengths and weaknesses, diagnose and document language and learning disabilities, and make intervention plans.

The intra-individual variations procedure has several advantages over traditional aptitude/achievement discrepancy procedures. It provides a more comprehensive evaluation because examiners can analyze a variety of scores across cognitive and achievement clusters. The intra-achievement variations procedure examines the difference between an individual's achievement score in a particular area with a prediction estimated based on an average of all other achievement areas to help professionals to identify learning disabilities, pinpoint specific problems, and choose the most appropriate intervention for an individual. The procedure is also particularly useful for identifying learning disabilities early, before a child fails in school.