BIOS601 AGENDA: Thursday September 04, 2014
[updated Sept 02, 2014]
Agenda for Thursday Sept 04, 2014
- Discussion of issues in the
Assignment on measurement
Q1 and Q2 (measuring 'Readability'): answers need not be handed in; just think about the issues;
If there is time, we might discuss and do some 'measuring' in class.
Q3, Q4, Q5, Q6, Q7, Q13: Answers to be handed in.
Q8, Q9, Q10, Q11, Q12: from last year; answers need not be handed in. If there's time,
we will think about what the answers might have looked like.
Remarks: this topic of measurement is probably new for you, as it was for JH
when he began in cancer clinical trials in 1973, and oncologists (cancer doctors)
were judging responses of advanced cancer to chemotherapy
by measuring tumours by
'palpation'.
Just because (random) measurement errors tend to cancel out in
averages doesn't mean that errors in measurement can be ignored. For example,
how comfortable would you be in measuring how much physical activity JH does
by having him wear a 'step-counter' for a randomly selected week of the
year, and using that 1-week
measurement as an 'x' in a multiple or logistic or Cox
regression? See slides 7 and 8 from part of JH's
"Scientific reasoning, statistical thinking, measurement issues, and use of
graphics: examples from research on children"
at Royal Children's Hospital in Melbourne, earlier this year.
pdf
Some of the the terminology will be new to you, and so (as you will discover
in your simulations of how well you can estimate the conversion factors between
degrees F and degrees C) will some of the consequences of measurement error.
The "animation (in R) of effects of errors in X on slope of Y on X" might be of interest,
as might the java applet accompanying "Random measurement error
and regression dilution bias".
These consequences are rarely touched on, yet alone emphasized, in theoretical courses on regression, where all
'x' values are assumed to be measured without error! Welcome to the REAL world.
For this exercise, and the topics it addresses, the most relevant portions of
the 'surveys' resources are
Measurement: Reliability and Validity and
Effects of Measurement Error