The NAEP Long-Term Trend Performance LevelsMore detailed information about what students know and can do in each subject area can be gained by examining their attainment of specific performance levels in each assessment year. This process of developing the performance-level descriptions is different from that used to develop achievement-level descriptions in the main NAEP reports. For each of the subject area scales, performance levels were set at 50-point increments from 150 through 350. The five performance levels—150, 200, 250, 300, and 350—were then described in terms of the knowledge and skills likely to be demonstrated by students who reached each level. A "scale anchoring" process was used to define what it means to score in each of these levels. NAEP's scale anchoring follows an empirical procedure whereby the scaled assessment results are analyzed to delineate sets of questions that discriminate between adjacent performance levels on the scales. To develop these descriptions, assessment questions were identified that students at a particular performance level were more likely to answer successfully than students at lower levels. The descriptions of what students know and can do at each level are based on these sets of questions. The guidelines used to select the questions were as follows: students at a given level must have at least a specified probability of success with the questions (75 percent for mathematics, 80 percent for reading), while students at the next lower level have a much lower probability of success (that is, the difference in probabilities between adjacent levels must exceed 30 percent). For each curriculum area, subject-matter specialists examined these empirically selected question sets and used their professional judgment to characterize each level. The reading scale anchoring was conducted on the basis of the 1984 assessment, and the scale anchoring for mathematics trend reporting was based on the 1986 assessment. The five performance levels are applicable at all three age groups, but only three performance levels are discussed for each age: levels 150, 200, and 250 for age 9; levels 200, 250, and 300 for age 13; and levels 250, 300, and 350 for age 17. These performance levels are the ones most likely to show significant change within an age across the assessment years and do not include the levels that nearly all or almost no students attained at a particular age in each year. Explore the long-term trend mathematics performance-level descriptions. Explore the long-term trend reading performance-level descriptions.
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