We have speculated that it is often easier to regard the difference between two
averages as a central tendency than it is to think of a single average that way. This
suggests, perhaps somewhat counterintuitively, that rather than beginning
instruction by having students explore single distributions of individual values, we
instead might fruitfully start with questions involving group comparison. Some
support for the benefit of having even young students grapple with comparison
problems comes from accounts from teachers of data analysis in the elementary
grades (Konold & Higgins, 2003). Similarly, all the problems in the middle-school
materials developed by Cobb, McClain, and Gravemeijer involve group comparison
(Cobb, 1999; Cobb, McClain, & Gravemeijer, 2003). As Watson and Moritz (1999)
pointed out, some of the benefits of comparison contexts are undoubtedly related to
their being more interesting and allowing students to see more clearly why the
question matters and why averages might be useful. But in addition, we expect that
in a comparison situation, students can more easily view averages of the individual
groups as summary measures of processes and can readily perceive the difference
between those measures as some signal rising through the din of variability.
We have speculated that it is often easier to regard the difference between two
averages as a central tendency than it is to think of a single average that way. This
suggests, perhaps somewhat counterintuitively, that rather than beginning
instruction by having students explore single distributions of individual values, we
instead might fruitfully start with questions involving group comparison. Some
support for the benefit of having even young students grapple with comparison
problems comes from accounts from teachers of data analysis in the elementary
grades (Konold & Higgins, 2003). Similarly, all the problems in the middle-school
materials developed by Cobb, McClain, and Gravemeijer involve group comparison
(Cobb, 1999; Cobb, McClain, & Gravemeijer, 2003). As Watson and Moritz (1999)
pointed out, some of the benefits of comparison contexts are undoubtedly related to
their being more interesting and allowing students to see more clearly why the
question matters and why averages might be useful. But in addition, we expect that
in a comparison situation, students can more easily view averages of the individual
groups as summary measures of processes and can readily perceive the difference
between those measures as some signal rising through the din of variability.
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