Graham recruited student volunteers to participate in his dissertation study. He set up several times for students to come to a specified classroom and read various types of instructional materials and to be tested. He ran all of his control conditions first and then for each session he placed all students at the session in the same treatment condition. This is problematic because those who volunteered early are likely different than those who volunteered later. This problem is primarily due toPGraham recruited student volunteers to participate in his dissertation study. He set up several times for students to come to a specified classroom and read various types of instructional materials and to be tested. He ran all of his control conditions first and then for each session he placed all students at the session in the same treatment condition. This is problematic because those who volunteered early are likely different than those who volunteered later. This problem is primarily due to:_______.A) error rates.B) sampling error.C) researcher bias.D) sampling bias.

Sampling bias refers to a scenario where conditions in the research give more subjects in the population of interest the chance to appear either more or less times than others instead of all the subjects having an equal chance of representation.

The students were to come in at different times yet Graham gave them all the same treatment conditions. This could lead to sampling bias because those who volunteered earlier are likely different from those who volunteered later.