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Study Design
Stats
Stats 2
Epidemiology+other
Random
100
Name the two major types of study design and an example for both.
What is 1. Observational 2. Experimental
100
BLANK is the proportion of truly diseased persons in the screened population who are identified as diseased by the screening test (i.e. they have high scores). BLANK indicates the probability that the test will correctly diagnose a case, or the probability that any given case will be identified by the test.
What is sensitivity
100
In 1989, 199 confirmed cases of meningococcal meningitis occurred in Ontario, yielding an incidence rate of 2.2 cases per 100,000 population. There were 20 deaths and 160 severe non-fatal cases. In this situation, the case fatality rate for meningococcal meningitis was roughly:
What is 10% The case fatality rate = (20 deaths / 199 confirmed cases) x 100% = roughly 10%. All of the other information in the question was extraneous.
100
Which of the following study designs is most appropriate for estimating the population prevalence of a disease?
What is a cross sectional study. Cross-sectional studies provide a snapshot of what is happening at a particular point in time, so can be used to estimate the frequency (prevalence) of a disease or other characteristic. This design can also be used to evaluate a new diagnostic procedure (sensitivity and specificity), but cannot be used to estimate incidence.
100
BLANK occurs when a factor other than the one you are studying is associated both with the disease and the factor you are studying. This can make it seem as though the factor you are studying causes the disease even if, in reality, it does not.
What is a Confounding factor
200
Give 2 reasons why you would choose to do an observational study instead of an experimental study?
1.When you merely want to collect descriptive information: "Is the incidence of diabetes rising?" 2.When you want to report on the causes of a problem without disturbing the natural setting (I want to find out why students do not attend lectures) 3.When you can't do an experiment: "How fast does the earth move around the sun?" 4.When it's not acceptable to do an experiment: "How much does not wearing a condom increase the likelihood of HIV infection?"
200
A BLANK is a measure of association between an exposure and an outcome. The BLANK represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.
What is the odds ratio
200
Researchers tested a new drug that aims to decrease the chance of stroke in men who experience atrial fibrillation. The study included 1,000 who took the new drug for 5 years, and 1,000 were given the standard therapy. At the end of the trial, 6% of the men in the standard therapy group experienced a stroke, compared to only 2% in the group taking the new drug. What is the relative risk reduction.
What is 0.66 or 2/3 RRR = (Control Event Rate − Experimental Event Rate) ÷ Control Event Rate (6%-2%) /6%
200
What is the difference between prevalence and incidence?
Prevalence "How many people actually have the disease at any point in time?" Prevalence = Number of people with the disease at a given time / Number of people at risk. Incidence: Number of new cases in a fixed time period / Number of people at risk. Usually the period of study is chosen to be one year, in which case we speak of the annual incidence.
200
BLANK refers to what conclusions we can draw from the results of a measurement. Introductory-level definitions are "Does the test measure what we are intending to measure?", or "How closely do the results of a measurement correspond to the true state of the phenomenon being measured?
What is Validity.
300
Name the 3 types of observational studies
What is 1.Cross-sectional surveys 2.Cohort 3.Case-Control
300
a test for comparing the mean values from two samples. It shows how confident we can be that the two mean values differ in the populations from which the samples were drawn. Using statistical jargon it shows how confident we can be in rejecting the null hypothesis that the two samples come from populations with identical mean values.
What is a t-test
300
To evaluate the performance of a new diagnostic test, the developer checks it out on 100 known cases of the disease for which the test was designed, and on 200 controls known to be free of the disease. Ninety of the cases yield positive tests, as do 30 of the controls. Based on these data, the specificity and false positive error rates of the test are, respectively,
What is 85% and 15%
300
Term that refers to consistency or dependability. For example your patient Jim is unpredictable; sometimes he comes to his appointment on time, sometimes he's late and once or twice he was early.
What is Reliability
300
What are the 3 components of the evidence based medicine triad that improve patient outcome.
What is 1. individual clinical experience. 2. best available clinical evidence and 3. patient's values and expectations
400
Name 3 limitations of an RCT.
1. Ethical concerns 2. Expenses 3.closely controlled conditions of a trial may not represent the real-life situations in which the medication will eventually be used
400
BLANK is the ratio of the risk of disease among people with a risk factor, to those without. This indicates of the strength of a risk, or causal, factor.
What is the relative risk
400
Among 10000 subjects allocated to active treatment for stroke prevention, there was 25 stroke. Among 10000 subjects allocated to placebo there were 175 strokes. What is the number needed to treat (NNT) to prevent a single stroke under the conditions of this trial?
What is 66.6
400
A statistical measure that shows how closely two variables lie in a linear association. This can range from -1 to +1, the two extremes denoting a perfect linear relationship and 0 denoting a complete absence of relationship.
What is a correlation coefficient
400
What are the typical phases of bringing a pharmaceutical product to market?
Phase I studies follow animal experimentation, and primarily determine how the drug works in humans: range of dosage and safety. Generally undertaken in healthy people. Phase II studies test efficacy and safety in small groups of patients with the condition (around 100). Phase III trials are much larger (thousands of patients with the condition) and are randomized trials comparing the medication with established treatments to show if it is safe and effective. The results of several randomized trials are often combined, sometimes using a systematic review and sometimes a meta-analysis. Phase IV studies come after a licence has been issued, and provide more information on longer-term safety and side effects, and also on how well it works with other conditions.
500
Name one advantage and one disadvantage of using a cohort study design.
A-Prospective, so can establish causal sequence, can estimate incidence D-Time consuming, costly
500
BLANK is a way of measuring the size of a difference between two treatments. It simply tells you how much better or worse one treatment is at reducing a particular outcome in terms of the actual numbers (or rates) of people who experience the outcome compared with another treatment.
What is the Absolute risk reduction (ARR)
500
There are 100 medical students who are studying vigorously for an exam and 100 art students enjoying their steady vacation . 20 of the medical students experience migraines whereas only 5 of the arts students had migraines. What is the estimated relative risk (RR), and what is the attributable risk (AR) of experiencing a migraine following a period of hard study for an exam?
What is RR:4 and AR 15 per 100
500
The apparent lengthening of survival due to earlier diagnosis in the course of disease without any actual prolongation of life can be explained by this type of bias.
What is the lead-time bias.
500
Please name in order of importance the The Hierarchy of Evidence. (Hint: think about the different study designs) there are 8 answers
What is 1.Meta-analyses of clinical trials (e.g. the Cochrane Collaboration reports) 2.High-quality systematic reviews or expert consensus statements (UptoDate, etc) 3.RCTs 4.Other clinical trials (quasi-experimental designs) 5.Prospective cohort studies 6.Historical cohort studies 7.Non-systematic reviews 8.Case studies