Compiling and comparing student test scores is a vital job for a classroom teacher, as graphs help teachers determine if student scores fit on a classic bell curve distribution. By creating a bar graph and then a bell curve, teachers know if their content is too easy or difficult for the students. As a teacher, you can calibrate your curriculum to adjust to your students' abilities.
Labeling the Bar Graph
The first step toward creating a vertical bar graph is to label the axes on the bar graph. In this case, the y-axis represents the number of students that scored within a specific range. The x-axis represents student test scores. Divide the test scores into five-point intervals from left to right, ranging from the lowest to the highest. Label the y-axis with intervals of 1 up to a maximum of 15. If you are comparing the test scores for an entire grade, label the y-axis with intervals of 2 up to a maximum of 50, depending on the size of the cohort. Label the x-axis in multiples of 5 such as 50 to 55, 55 to 60, 60 to 65 and so on.
Ordering the Test Scores
Organize the test scores in numerical order, from the greatest to the least. After organizing the scores, divide them into groups, using the five-point intervals set up in the bar graph. Count the number of test scores in each grouping. If a test score fits into two different groups, such as a score of 95 -- which can fit in the 90 to 95 group or in the 95 to 100 group -- count that score as one-half a point in one group and one-half in the other group.
Creating the Bar Graph
Once your test score data is organized into five-point intervals, count the number of scores in each group. Draw the vertical bars that correspond to each group. The tallest bars should be exactly in or near the middle of the bar graph. If the tallest bars are toward the right, the students scored exceptionally well. In this case, the test was too easy for the students and the curriculum should be more challenging. If the tallest bars are located toward the left of the bar graph, the test was either too challenging or the material needs to be retaught, since the test scores were extremely low.
Creating the Bell Curve
A vertical bar graph of test scores should roughly correspond to a bell curve. In statistics, a bell curve represents the standard score and its deviations, with the highest part of the graph -- the bell -- representing the mean, or average score on the test. Most test scores should fit within two standard deviations of the mean. If your bar graph has its highest bars in or near the middle of the graph and its lowest bars on the extreme left and right, the teacher has a bell curve distribution and the instruction is on target. Draw a curve connecting the top of each bar from left to right to complete the graph.
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