Introduction to Epidemiology Flashcards
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
Because there are relatively few patients in this study, it may give a misleading impression of the actual effectiveness of surgery.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
D
Samples can give a misleading impression of the situation in the parent population, especially if the sample is small.
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
The results of this study may not apply to your patient, a woman, because all the patients in the study were men.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
E
Generalizing the results of a study of men to the care of a woman assumes that the effectiveness of surgery for low back pain is the same for men and women.
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
The patients who were referred for surgery were younger and fitter than those who remained under medical care.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
A
The difference in recovery between patients who received surgery versus medical care may be the result of some other factor, such as age, that is different between the two treated groups and not the result of surgery itself.
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
Fewer patients who did not have surgery remained under care at the clinic two months after surgery.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
B
The two treatment groups did not have an equal chance of having pain measured.
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
Compared with patients who had medical care alone, patients who had surgery might have been less likely to report whatever pain they had and the treating physicians less inclined to record pain in the medical record.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
B
There are biases related to the measurement of the outcome (recovering from pain)
COMPLETE SAMPLEX
A 37-year-old woman with low back pain for the past four weeks want to know if you recommend surgery. You prefer to base your treatment recommendations on research evidence whenever possible. In the strongest study you can find, investigators reviewed the medical records of 40 consecutive men with low back pain under care at their clinic. Twenty-two had been referred for surgery and the other 18 patients had remained under medical care without surgery. The study compares rates of disabling pain after 2 mos. All of the surgically treated patients and 10 of the medically treated patients were still being seen in the clinic throughout this time. Rates of pain relief were slightly higher in the surgically-treated patients.
Patients without other medical conditions were both more likely to recover and more likely to be referred for surgery.
A. Selection bias B. Measurement bias C. Confounding bias D. Chance E. External validity (generalizability)
C
The other medical conditions confound the relationship between treatment and outcome; that is, they are related to both treatment and recovery and might be the reason for the observed differences.
COMPLETE SAMPLEX
Histamine is a mediator of inflammation in patients with allergic rhinitis (“hay fever”). Based on this fact, which of the following is true?
A. Drugs that block the effects of histamines will relieve symptoms.
B. A fall in histamine levels in the nose is a reliable marker of clinical success.
C. Antihistamines may be effective and their effects on symptoms (such as itching nose, sneezing and congestion) should be studied in patients with allergic rhinitis.
D. Other mediators are not important.
E. If laboratory studies of disease are convincing, clinical research is unnecessary.
C
The observation that histamines mediate inflammation in hay fever leads to a promising hypothesis that blocking histamines will relieve symptoms, but the hypothesis needs to be tested in people with hay fever. The other answers all assume more about the causes of symptoms than is actually stated. For example, histamine is only one of many mediators of inflammation in hay fever.
COMPLETE SAMPLEX
Samples of populations may have characteristics that differ from the population because of random variation. T/F
T
Samples may misrepresent populations by chance, especially when the samples are small.
COMPLETE SAMPLEX
Samples of populations are the only feasible way of studying the population. T/F
T
In nearly all situations, populations are too large to study without sampling
COMPLETE SAMPLEX
Samples of populations should be selected in a way that every member of the population has an equal chance of being chosen. T/F
T
When they are possible, random samples are best because they remove bias, although chance differences between samples and population may remain.
COMPLETE SAMPLEX
You are making a treatment decision with a 72-year-old man with colon cancer. You are aware of several good studies that have shown that a certain drug combination prolongs the life of patients with colon cancer. However, all the patients in these studies were much younger. Relying on those studies for your particular patient…
is a matter of personal judgement. T/F
T
Generalizing from younger to older patients is a matter of personal judgement based on whatever facts there are that bear on how the two might respond to the same treatment, until a study of older patients becomes available.
COMPLETE SAMPLEX
You are making a treatment decision with a 72-year-old man with colon cancer. You are aware of several good studies that have shown that a certain drug combination prolongs the life of patients with colon cancer. However, all the patients in these studies were much younger. Relying on those studies for your particular patient…
is called internal validity. T/F
F
Internal validity is about whether the results are correct for the patients in the study, not about whether they are correct for other kinds of patients.
COMPLETE SAMPLEX
You are making a treatment decision with a 72-year-old man with colon cancer. You are aware of several good studies that have shown that a certain drug combination prolongs the life of patients with colon cancer. However, all the patients in these studies were much younger. Relying on those studies for your particular patient…
is affected by chance but not bias. T/F
F
Both bias and chance affect internal validity, which in turn affect whether the results are true for anyone, young or old.
COMPLETE SAMPLEX
A group of fitness first clients was compared to the community as to their knowledge of antioxidants in preventing viral infections.
A. Selection bias B. Confounding bias C. Measurement bias D. Chance E. Random Variation
A
COMPLETE SAMPLEX
MRI was busted so they used a CT scan to diagnose the disease
a. selection bias b. chance c. measurement bias d. random variation
C
COMPLETE SAMPLEX
Divergence of the observation of the sample from the true population due to chance alone…
a. bias b. confounding c. random variation d. sampling error e. external validity
C
COMPLETE SAMPLEX
The main goal of randomization in clinical trials is
A. To make sure that the participant will have equal chances of getting into either treatment arm
B. To make the 2 groups equal
C. To make sure that the outcome is due to the interventions and not from any extraneous variable
D. AOTA
E. Only A and C
D
