THE IMPACT OF TEXTBOOK CONCEPT EMPHASIS ON THE LEARNING OF BIOLOGICAL CONCEPTS AT DIFFERENT COGNITIVE LEVELS BY HIGH SCHOOL STUDENTS
The study was based on the information about the important roles of textbooks and objectives in the textbook as disclosed in the status studies and the study by the biology focus group of Project Synthesis. The basic measure for the study was 17-year-old students' achievement level as measured by NAEP in 1976-77. An additional tool for the study was the behavioral objective as listed in the three most widely used high school biology textbooks and a projected biology textbook. The study was designed to investigate the following factors: a difference among mean achievement levels of biology exercise items at four cognitive levels, any relationship between concept emphasis and achievement level at different cognitive levels, an interaction on achievement level of concept emphasis with cognitive level, and any change in concept emphasis in high school biology textbooks since the status studies and synthesis study. The biology exercise items were classified by a panel of 13 external experts into each of ten conceptual areas. Then, achievement levels were assigned into one of the four cognitive levels as classified by NAEP and into one of the ten conceptual areas on the basis of the panel's judgement. The panel also classified the objectives from the three most widely used textbooks and from a projected textbook into one of the ten conceptual areas. The objectives from the three textbooks were combined to form a list of objectives for a hypothetical integrated textbook. In this objective list, concept emphasis was estimated by dividing the number of objectives in each conceptual area by the total number of objectives. The major findings were as follows: (1) There were significant differences among achievement levels at cognitive levels. (2) There were significant relationships between achievement level and concept emphasis except at the cognitive level, defined as comprehension. (3) There was no interaction effect, although there were significant effects of cognitive level and concept emphasis on achievement level. However, when difficulty effect was eliminated, there were significant main and interaction effects on achievement level for difficult test items. (4) Change in concept emphasis had taken place in at least one of the recently published biology textbooks.
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