Lecture 7 (Prof Rovina)
Video 1: Planning the measurements (precision, accuracy, and validity)
Phenomena will be analyzed statistically. Garbage in  garbage out.
Validity of the study ditentukan oleh variables. Jika mau tau kanker prostat yaitu ukur PSA, drug
concentration utk drug trial. Measurement scale: pakai alat apa, jenis variable nya apa
Type
exp
Categorial nominal
Gender, blood
type
Categorical ordinal
Degree of pain
Continuous/discrete Weight, BMI
Descriptive stat
Count, %
Information
content
Lower
Above, median
Above, means, SD
Intermediate
Higher
Measurement scale: what to choose?
Video 2:
Measurement: precision and accuracy
Precise measurement: reproducibility, reliability, consistency
Free/lack of random error (variability)
Based on sample size
Quantified as confident interval (CI)
Accurate measurement (validity)
Free/lack of systematic error (bias)
External validity
How to improve?
Enhancing precision: standardizing the measurement methods (SOP), training and certifying the
observers, refining the instruments, automating the instruments, repetition of measurement.
Enhancing accuracy: blinding, calibrating the instrument, making unobtrusive measurement (subject
unaware of being observed)
In clinical trial:
QA quality assurance: to think ahead before error happen, membuat SOP
QC: to act after error happens and how to prevent it in the future (CAPA  correction action prevention
action)
Clinical monitoring: to make sure research is conducted according to the approved protocol and GCP