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Bias (FA12 p56) (FA13 p53) (SU13 p41)Statistical distribution (FA12 p57) (FA13 p54) (SU13 p42-43)Null hypothesis (FA12 p57) (FA13 p54) (SU13 p43)Error (FA12 p57) (FA13 p54) (SU13 p43)Power (FA12 p58) (FA13 p55)

Bias and Error

3 Question Warm-up1. Which hormones share a common alpha subunit? (SU13 p143)

2. What is the difference between a case-control study, a cohort study, and a clinical trial? Which studies use odds ratios, and which use relative risks? (FA12 p52) (FA13 p50) (SU13 p41)

3. Which neoplasm is most commonly responsible for each of the following hormone paraneoplastic syndromes? (FA12 p255) (FA13 p223) ACTH Cushing syndrome PTH-related peptide hypercalcemia Erythropoietin polycythemia ADH SIADH

4. Examples of Bias: Selection bias The referral centers for a trial of a new anticancer drug have more patients

with end stage disease than early stage, so more patients with end stage disease are referred for the trial than early stage disease.

Berksons bias Studies performed on patients that have been hospitalized type of selection bias

Recall bias Parents of autism patients having a more detailed recall of events and illnesses in their childs first two years of life compared to parents of healthy controls.

Sampling bias A study performed in China may not be generalizable to the US population. Late-look bias Sending a survey out to people diagnosed with a fatal illness 5 years after

diagnosis will preferentially sample those with a low grade disease (or few comorbidities) Procedure bias The positive benefit of a new drug during a study simply may have been

due to the fact that study participants were required to attend clinic monthly, where they received extra disease education and counseling compared with the controls.

Confounding bias Are asbestos miners more likely to have cancer because they mine asbestos or because they are more likely to smoke?

Lead-time bias While test PSA-xyz may detect prostate cancer before it is detected by a traditional PSA, early detection using PSA-xyz does not increase cancer survival compared to traditional PSA.

Pygmalion effect An orthopedic surgeon investigator who finds statistically significant benefit of arthroscopic surgery when compared to non-invasive therapeutic strategies. A chiropractor-led study that finds significant benefit of the effects of cervical manipulation when compared to traditional medicine strategies.

Hawthorn effect When studying the effects that infection control education has on physicians, the investigator notes that both the experimental and the control groups improve their hand hygiene.

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end of session Quiz5. Study X shows that vitamin C can prevent Coronavirus infections, but 10 other

studies show no benefit. What type of error is found in study X? (FA12 p57) (FA13 p54) (SU13 p43)

6. Study Y shows that aspirin administration during an MI offers no improvement in patient morbidity or mortality. What type of error is present? (FA12 p57) (FA13 p54) (SU13 p43)

7. What is the difference between the mean, median, and mode? (FA12 p57) (FA13 p54) (SU13 p42)

8. What does it mean to say that a statistical distribution has a positive skew? (FA12 p57) (FA13 p54) (SU13 p42)

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