Here are some relevant passages from the published Sadler survey. I looked
for all references to the word textbook:
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Selection of a physics textbook is a very visible decision that a teacher
can make and there seems no end to the advertisements and promotional
materials that publishers provide to teachers to hawk their products.
Authors spend years creating new texts and updating old ones. This study
found no significant difference in college physics grades among any
of the major texts used in high school physics. While there may be a
difference between alternative treatments or topics covered, this study
failed to reveal it. In fact, those teachers who choose not to use a text
appear to have a real advantage. Perhaps these teachers are freed from the
most obvious rubric for measuring how much they have covered and must decide
on which central ideas to pursue. Perhaps they use materials that they have
written themselves or have been given to them by other teachers or
researchers. Students often rely heavily on the authority of textbook,
either looking for key words or unconnected facts to answer questions. In
contrast, students are more likely to find their answers in class notes or
their own real world experiences if the text is not central (Anderson,
1992). In any event, avoiding reliance on a text appears to have a
significant association with higher grades in introductory college physics.
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Students in more rigorous high school physics courses, on average, perform
better in introductory college physics; however, there is more variation
within these courses than between them. The predictive power of the type of
course (regular, honors, or AP) is subsumed by specific pedagogical
variables when included in regression models. Students appear to do better
in college physics if they have taken rigorous high school physics courses,
where their teachers concentrated on fewer concepts, covering less material,
but in greater depth. Students in regular physics courses with these same
characteristics have equaled or surpassed the performance students in more
rigorous courses. In particular, deferring to a textbook for the structure
and pace of a high school course was not supported as a viable strategy.
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Notice that Sadler says PERHAPS they use materials they have written
themselves. He does not make any reference to extensive written materials.
So he apparently does not have much evidence for the prepared extensive
notes provided to the students, or his evidence/analysis shifted between the
talk and publication.
[Example of what Sadler said: The success without a text book often came
from classes where the instructor had basically prepared extensive notes and
provided them to the class--essentially a 'book'. I may be wrong, but as I
recall, much of the evaluation here was by grades, or success in a College
course to evaluate the High School course.]
This brings up another discrepant factor. We remember what we believe and
forget what we don't. Memory is not photographic and is extremely
unreliable in certain details. We only store what we consider to be
important details and then reconstruct the rest of the memory according to
our paradigms and experiences. So it is possible that the "extensive notes"
may have been a misremembered detail. Ronald Regan was a master of this, as
actors often are. He once said when challenged as to the veracity of a
story "but it sounds true". I have actors in the family, so I know from
first hand experience how that can work.
Maybe he published this elsewhere???? In either case it is always wise to
consult the literature and the research directly!