Item Development – Planning your field test study
Once the items have passed their final editorial review, they are ready to be delivered to participants, but they are not quite ready to be delivered as scored items. For large-scale assessments, it is best practice to deliver your new items as unscored field test items so that you can gather item statistics for review before using the items to count toward a participant’s score. We discussed field test studies in an earlier post, but today we will focus more on the operational aspects of this task.
If you are embedding field test items, there is little you need to do to plan for the field test, other than to collect data on your participants to ensure representativeness and to make sure that enough participants respond to the item to yield stable statistics. You can collect data for representativeness by using demographic questions in Questionmark’s authoring tools.
If field testing an entire form, you will need to plan your field test carefully. When an entire form is going to be field tested, Schmeiser and Welch ( Educational Measurement, 4th ed.) recommend testing twice as many items as you will need for your operational form.
To check representativeness, you may want to survey your participants in advance to help you select your participant sample. For example, if your participant population is 60% female and 40% male, but your field test sample is 70% male, then that may impact the validity of your field test results. It will be up to you to decide which factors are relevant (e.g., sex, ethnicity, age, level of education, location, level of experience). You can use Questionmark’s authoring tools and reports to deliver and analyze these survey results.
You will also need to entice participants to take your field test. Most people will not want to take a test if they do not have to, but you will likely want to conduct the field test expeditiously. You may want to offer an incentive to test, but that incentive should not bias the results.
For example, I worked on a certification assessment where the assessment cost participants several hundred dollars. To incentivize participation in the field test study of multiple new forms, we offered the assessment free of charge and told participants that their results would be scored once the final forms were assembled. We surveyed volunteers and selected a representative sample to field test each of the forms.
The number of responses you need for each item will depend on your scoring model and your organization’s policies. If using Classical Test Theory, some organizations will feel comfortable with 80 – 100 responses, but Item Response Theory models may require 200 – 500 responses to yield stable item parameters.
More is always better, but it is not always possible. For instance, if an assessment is for a very small population, you may not have very many field test participants. You will still be able to use the item statistics, but they should be interpreted cautiously in conjunction with their standard errors. In the next post, we will talk about interpreting item statistics in the psychometric review following the field test.