Iowa Tests of Basic Skills

Uses of the Iowa Standardized Assessments

The Iowa Tests (referred to as the ITBS in this entry) is a group-administered norm-referenced achievement test, designed to compare individual student achievement scores to those of a representative norm group of peers. The design of norm-referenced tests enables educational leaders, parents, and state policy makers to compare students with other students who are in the same norm group. For example, the available norms for the ITBS include districts of similar sizes, regions of the country, socioeconomic status, ethnicity, and type of school, in addition to a representation of students nationally. By comparing to a normative sample, the Iowa Assessments, like most standardized assessment tests, allow districts to gather data to improve, differentiate, and personalize instruction for all students.

The ITBS subtests include vocabulary, reading comprehension, mathematics, social studies, science, and other sources of information such as maps and diagrams. The Iowa Tests Assessments meet most states’ requirements for an annual, nationally normed standardized test for assessing student academic progress in various content areas. The ITBS, like most other respected standardized achievement tests, meet certain psychometric markers and standards for reliability, validity, and analysis of the absence of bias, explained in the next section.

Validity and Reliability of the Iowa Tests

The ITBS have been proven to be technically sound, with many years of research on reliability and validity having been conducted by researchers at the University of Iowa as well as by other scholars who have used the ITBS to measure academic progress in various content areas. The ITBS include a broad variety of item types and are designed based on research regarding their validity and reliability.

Reliability refers to the amount of random variability in the scores produced by an assessment. [Page 878]Could a student take it again and achieve a similar or same score? Validity means that the test measures accurately what it is intended to measure. In addition, valid tests must be unbiased, meaning students must not be disadvantaged by where they live or by their individual or group characteristics. Valid assessment of achievement using the ITBS for a particular school is one that matches the school’s education standards and learning outcomes. That is, the skills and content knowledge that contribute to success in the ITBS should be similar to the skills and knowledge that are taught in the school or district that has decided to use the Iowa Assessments. Whether the match is appropriate is something that can only be determined by a careful analysis of the test items early in the decision-making process.

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