# GLOSSARY

**Age Percentile Rank**

The stanine scale is a normalized standard score scale consisting of nine broad levels designated by the numbers one through nine. A percentile rank indicates the percentage of students in the same age group whose scores fall below the score obtained by a particular student. For additional details see Percentile Rank.

**Age Stanine (AS)**

A stanine indicating the status or relative rank of a student’s score compared with a nationally representative sample of examinees of a similar age. For additional details see Stanine.

**Grade-Based Norms**

Developed for the purpose of comparing a student's score with the scores obtained by other students in the same grade on the same test. How much a student knows is determined by the student's standing or rank within the grade level score distribution.

For example, a norms table for the 6th grade would provide information such as the percentage of 6th grade students (based on a nationally representative sample) who scored at or below each obtainable score value on a particular test. Compare to Age-Based Norms.

**Grade Equivalent**

The grade equivalent is a number that describes a student's location on an achievement continuum. Grade Equivalents are expressed in terms of grade and months into grade, assuming a 10-month school year (e.g., 8.4 means after 4 months of instruction in the 8th grade). The Grade Equivalent corresponding to a given score on any test indicates the grade level at which the typical student obtains this score. Because of this, Grade Equivalents are not based on an equal interval scale, and therefore cannot be added, subtracted, or averaged across test levels the way other scores can (scale scores or standard scores).

Interpretations/Cautions of Grade Equivalent Scores: If a sixth-grade student obtains a GE of 8.4 on the Vocabulary Test, his/her score is like one a typical student finishing the fourth month of eighth grade would likely get on the Vocabulary Test. Grade Equivalents are particularly suited for estimating a student's developmental status or year-to-year growth. These scores are not particularly suited for identifying a student's standing within a group or for diagnosing areas of relative strength or weakness. Grade Equivalents do not provide a prescription for grade placement. For example, a fourth-grade student earning a GE of 6.2 on a fourth-grade reading test obviously demonstrates that his/her developmental level in reading is high relative to his/her fourth-grade peers. However, the test results supply no information about how well he/she would handle the material normally read by students in the early months of sixth grade. It, therefore, cannot be concluded that he/she is ready for placement in the sixth grade.

**Grade Percentile Rank (GPR or PR)**

A percentile rank indicating the status or relative rank of a student’s score compared with a nationally representative sample of examinees of a similar grade. For additional details see Percentile Rank.

**Grade Stanine (GS)**

A stanine indicating the status or relative rank of a student’s score compared with a nationally representative sample of examinees of a similar grade. For additional details see Stanine.

**Local Norms**

Norms (i.e., percentile ranks and stanines) by which test scores are referred to a specific, limited reference population of particular interest to the test user (e.g., norms group is based on state, district, or school data) and are not intended as representative of populations beyond that particular setting. Used to evaluate a student's performance on a test in comparison to other students within the same subpopulation of interest.

**Local Percentile Rank**

Percentile rank based on the district’s or school’s own data as opposed to the national-based normative information. For additional details see Local Norms and Percentile Rank.

**Local Stanine**

A stanine based on the district's or school’s own data as opposed to the normative information based on a national sample. For additional details see Local Norms and Stanine.

**NATIONAL PERCENTILE RANK (NPR)**

A Percentile Rank indicating the status or relative rank of a student's score compared to a nationally representative sample of examinees. For additional details see Percentile Rank.

**National Stanine (NS or Sta9)**

A stanine score indicating the status or relative rank of a student's score compared to a nationally representative sample of examinees. For additional details see Stanine.

**Normal Curve Equivalent (NCE)**

Normalized standard scores that range in value from 1 to 99, and have a mean of 50 and a standard deviation of 21.06. In order to interpret these scores it is often necessary to relate them to other scores such as percentile ranks or stanines. NCE's can be thought of as roughly equivalent to stanines to one decimal place. For example, an NCE of 48 may be interpreted as a stanine of 4.8. One advantage to NCE's is that they have the properties of an equal interval score, which means they can be averaged, unlike Percentile Ranks. Another advantage to NCE scores is that all test publishers derive these scores in the same way, which leads to some comparability in reporting procedures.

**Normal Distribution**

Also known as the bell-shaped curve because of its distinctive appearance in that scores are distributed symmetrically about the middle, such that there are an equal number of scores above as below the mean, with more scores concentrated near the middle than at the extremes. The normal distribution is a theoretical distribution defined by specific mathematical properties that many human traits and psychological characteristics appear to closely approximate (e.g., height, weight, intelligence, etc.). Some features of the normal distribution are:

- The mean, median, and mode are identical in value.
- The scores are distributed symmetrical about the mean (50.0% above the mean and 50.0% below the mean).
- 68.26% of the scores are within 1 standard deviation of the mean (34.13% above the mean and 34.13% below the mean).
- 95.44% of the scores are within 2 standard deviations of the mean (47.72% above the mean and 47.72% below the mean).
- 99.72% of the scores are within 3 standard deviations of the mean (49.86% above the mean and 49.86% below the mean).

**Percent Correct**

The percentage of the total number of points that a student received on a test. The percent correct score is obtained by dividing the student's raw score by the total number of points possible and multiplying the result by 100. For multiple-choice tests, this is the same as dividing the student's raw score by the number of questions (i.e., each item is worth one point) and multiplying by 100. Percent Correct scores are typically used in criterion-referenced interpretations and are only helpful if the overall difficulty of the test is known.

**Percentile**

The score or point in a score distribution at or below which a given percentage of scores fall. For example, if 72 percent of the students score at or below a score of 25 on a given test, then the score of 25 would be considered at the 72nd percentile.

**Percentile Band**

A type of confidence interval, constructed around the examinee's obtained Percentile Rank, indicating with a given probability or confidence, the range of scores in which the examinee's true score may lie. Typically represented on score reports as the shaded area or band, around the obtained Percentile Rank (signified by a diamond or other symbol), extending from one (or more) standard error(s) of measurement below the obtained score to one (or more) standard error(s) of measurement above the obtained score.

**PERCENTILE RANK (PR)**

The percentage of scores in a specified distribution that fall at or below the point of a given score. Percentile Ranks range in value from 1 to 99, and indicate the status or relative standing of an individual within a specified group (e.g., norms group), by indicating the percent of individuals in that group who obtained lower scores. For example, if a student earned a 72nd Percentile Rank in Language, this would mean he or she scored better than 72 percent of the students in a particular norm group who were administered that same test of Language.

The percentile rank of a score is the percentage of scores in its frequency distribution that are equal to or lower than it. For example, a test score that is greater than or equal to 75% of the scores of people taking the test is said to be at the 75th percentile, where 75 is the percentile rank. Note: an individual's percentile rank can vary depending on which group is used to determine the ranking. A student is simultaneously a member of many groups: classroom, grade, building, school district, state, and nation. Test developers typically publish different sets of percentile ranks to permit schools to make the most relevant comparisons possible.

**Raw Score (RS)**

The first unadjusted score obtained in scoring a test. A Raw Score is usually determined by tallying the number of questions answered correctly, or by the sum or combination of the item scores (i.e., points). However, a raw score could also refer to any number directly obtained by the test administration (e.g., raw score derived by formula-scoring, amount of time required to perform a task, the number of errors, etc.). In individually administered tests, raw scores could also include points credited for items below the baseline. Raw Scores typically have little meaning by themselves. Interpretation of Raw Scores requires additional information such as the number of items on the test, the difficulty of the test items, norm-referenced information (e.g., Percentile Ranks, Grade Equivalents, Stanines, etc.), and/or criterion-referenced information (e.g., cut -scores).

**Standard Age Scores (SAS)**

Normalized standard scores, having a mean of 100 and a standard deviation of 16, provided for each battery and composite on the Cognitive Abilities Test (CogAT). These scores are developed for the purpose of comparing the rate and level of cognitive development of an individual to other students in the same age group. The Standard Age Score can be converted to other derived scores such as Age Percentile Rank (APR) and Age Stanine (AS) through the use of a set of conversion tables.

**Standard Score (SS)**

Standard scores are continuous across all levels and forms of a specific test. Because they are built on equal-interval scales, the magnitude of a given difference between two scores represents the same amount of difference in performance wherever it occurs on the scale. For example, the difference between standard scores of 15 and 20 is the same as the difference between standard scores of 45 and 50.

**Stanine**

The name stanine is simply a derivation of the term "standard-nine" scale. Stanines are normalized standard scores, ranging in value from 1-9, whose distribution has a mean of 5 and a standard deviation of 2. Stanines can, more easily, be thought of as coarse groupings of percentile ranks, and like percentile ranks indicate the status or relative rank of a score within a particular group. Due to their coarseness, stanines are less precise indicators than percentile ranks, and at times may be misleading (e.g., similar PR's can be grouped into different stanines [e.g., PR=23 and PR=24] and dissimilar PR's can be grouped into the same stanine [e.g., PR=24 and PR=40]). However, some find that using stanines tends to minimize the apparent importance of minor score fluctuations, and are often helpful in the determination of areas of strength and weakness.

**Universal Scale Score (USS)**

The Universal Scale Score provides a continuous growth scale of cognitive development from kindergarten through grade 12 for the Cognitive Abilities Test (CogAT). The USS is the standard score that is used for entry to the age and grade norms tables to obtain such derived scores as the Standard Age Score (SAS) and the Grade Percentile Rank (GPR) for each battery and composite score. These scores can then be converted to other derived scores such as Age Percentile Rank (APR), Age Stanine (AS), and Grade Stanine (GS) by the use of another set of conversion tables.

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