What is the [mean, median, mode] of the following distribution:
[25-30 two-digit numbers in random order]? (non-statistical
calculators allowed).
By plugging in different values for the variable elements, multiple
tasks can be generated from the shell. If the variable elements are
consistent in important characteristics including those that affect
difficulty, the tasks might possibly be reasonably parallel. Experience
has shown, however, that small variations in tasks generated by the
same shell can lead to large differences in difficulty.
In addition to the framework and the variable elements, task
shells may contain 1) a statement of the KSAs to be measured by the
task; 2) the directions that apply to the tasks generated by the shell;
3) specifications for any stimulus material to be provided with the
task; 4) for multiple choice tasks, rules for generating distracters;
and 5) general scoring rubrics for constructed response tasks, to be
augmented by prompt-specific scoring rules as necessary. Although
the logical flow appears to be to create a task shell and use it to
create tasks, ECD does not require strict adherence to a sequence of
steps. Some test developers have found it very useful to work
“backwards” from existing exemplary tasks to create task shells, and
many successful tasks are created in the absence of task shells.
If task shells are successful at identifying and holding constant
the elements in a task that affect its difficulty and discrimination, it
may be possible to reduce pretesting requirements because
pretesting a sample of tasks generated by the shell would provide
data that could be applied to all of the tasks generated by the shell.
It is an empirical question whether or not the pretested sample of
tasks generated by the shell will be similar enough in their operating
characteristics to reduce the need to pretest all of the tasks generated
by the shell. If the variable elements can be sufficiently specified,
task shells can facilitate the automated generation of tasks.