Joseph Maxwell (1992) offers a useful typology for understanding validity. His goal is to
provide a checklist of “threats” to validity. He identifies these categories of validity useful in
qualitative studies: Descriptive, interpretive, theoretical, generalizability. The categories
reformulate the traditional validity, reliability, generalizability categories which actually come
from quantitative research. Maxwell’s categories can be useful in analyzing the validity of this
study.
Descriptive Validity
Descriptive validity asks if the account of the research is factually accurate. For example,
are the transcripts an accurate rendering of the original videotapes? In an attempt to be
descriptively valid, I checked the transcripts against the video, not once, but several times. If an
interpretive questions arose, I found the episode on the video and carefully watched it while
making annotations. Moreover, the transcripts themselves were repeated edited. Where
important, I noted the antecedents of pronouns so the reader would know to what “it” refers. The
written solutions were the source of drawings incorporated in the annotated transcripts. It was
important to reproduce their drawings as accurately as possible. In many cases I watched the
video repeatedly to see exactly what they were drawing at a given instant. My comments about
Group 4C’s seating was based on observing their seating arrangement on the video as well as my
own personal observation of the group when they were solving the problem. The use of a video
source as opposed to an audio source for the basic data is the primary guarantor of descriptive
validity in this study.
Other descriptive aspects of the data are also accurate. The quiz grades for the students
in these two courses were obtained directly from the department’s master spreadsheet containing
the grades. The few statistical analyses in this research were made with generally accepted