Bias
A type of validity that implies the ability to generalize beyond a set of observations to some universal statement
What is external validity?
Is this probabilistic or deterministic causality?
A type of causality that claims that a cause is invariably followed by an effect
What is deterministic causality?
What type of blinding was used?
The researchers randomly gave 50 participants a placebo vaccine and 50 participants a new flu vaccine. The participants did not know which vaccine was which but the researchers did.
Single Blind
Is the study below an example of a prospective cohort or a retrospective cohort?
Researchers recruited 1,000 pregnant women at the start of their pregnancies. The women were asked to report their alcohol consumption throughout their pregnancies to observe the effects of alcohol on the development of birth defects.
Prospective cohort
What is A in a 2x2 table of the following study?
Researchers conducted a study on whether pesticide use causes an increased risk of developing Parkinson’s disease. They enrolled 200 people diagnosed with Parkinson’s disease and 200 controls in the study. Among the 200 patients diagnosed with Parkinson’s disease, 120 had pesticide exposure. Among the 200 controls, 60 had pesticide exposure.
A = 120
What is the missing criteria for confounding?
Be a risk factor for the disease,
Be associated with the exposure
Not be an intermediate step in the causal path between exposure and disease
Identify the causal type (A, B, C, or D) that the association most likely represents.
A. Necessary and Sufficient
B. Necessary but not Sufficient
C. Sufficient but not Necessary
D. Neither Necessary nor Sufficient
High cholesterol [X] is associated with heart attacks [Y].
D. Neither Necessary nor Sufficient
Is this a prophylactic trial or a therapeutic?
COVID-19 vaccines were given to 1,000 people of the general population to test if it effectively prevented the spread of disease.
Prophylactic
Is the study below an example of a population based cohort or an exposure based cohort?
Researchers studied 1,000 children born in 2016 for 10 years to examine the effects of air pollution on the development of asthma.
Population based cohort
What is D in a 2x2 table of the following study?
Researchers conducted a study on whether pesticide use causes an increased risk of developing Parkinson’s disease. They enrolled 200 people diagnosed with Parkinson’s disease and 200 controls in the study. Among the 200 patients diagnosed with Parkinson’s disease, 120 had pesticide exposure. Among the 200 controls, 60 had pesticide exposure.
D = 140
How would you fix random error in a study?
Increase sample size or the number of measurements
Identify the causal type (A, B, C, or D) that the association most likely represents.
A. Necessary and Sufficient
B. Necessary but not Sufficient
C. Sufficient but not Necessary
D. Neither Necessary nor Sufficient
Contact with Escherichia coli bacteria [X] is associated E.coli infection [Y].
B. Necessary but not Sufficient
What phase of clinical trials is this study in?
Researchers carefully select 150 participants who are then randomly given a placebo or the new medication to observe side effects of the medication.
Phase II
What type of study would you use to study the etiology of rare diseases?
Case control
Researchers studied whether daily energy drink consumption causes an increase in blood pressure. They recruited 150 daily energy drink consumers and 150 people who never consume energy drinks. 80 of the daily energy drink consumers and and 45 of the people who never consume energy drinks had high blood pressure.
Calculate the appropriate relative measure of effect and interpret it.
Odds Ratio = (AD) / (BC) = (80*105) / (70*45) = 2.667
Daily energy drink consumers are 2.67 times more likely as people who do not consume energy drinks daily to have high blood pressure.
The odds of high blood pressure are 167% higher among daily energy drink consumers compared to people who do not consume energy drinks daily.
What kind of bias would you be most concerned about in the study below?
A study is conducted about blood pressure and coffee consumption. Participants were asked how often they drank coffee on each day over the past 3 months.
Recall bias
Give an example of the sufficient-component cause model for hypertension. (List 3 component causes)
Family history
Sedentary lifestyle
High sodium diet
High alcohol intake
Chronic stress
What type of trial is this?
Researchers want to examine whether education about stagnant water in addition to the use of mosquito nets reduces dengue fever cases. They provided one town with educational materials and mosquito nets. The other town only received mosquito nets. They monitored cases of dengue fever in both towns for 3 years.
Community Trial
What type of study would you use to study prevalence at a single point in time?
Cross sectional
Researchers studied whether daily energy drink consumption causes an increase in blood pressure. They recruited 150 daily energy drink consumers and 150 people who never consume energy drinks. 80 of the daily energy drink consumers and and 45 of the people who never consume energy drinks had high blood pressure.
Calculate the appropriate absolute measure of effect and interpret it.
Risk difference = [A/(A+B)] - [C/(C+D)] = [80/150] - [45/150] = 0.23
Daily energy drink consumption results in an excess of 0.23 cases of high blood pressure in the exposed group.
If daily energy drink consumption were eliminated, there would be 0.23 fewer cases of high blood pressure in the exposed group.
What are 3 ways to control confounding error?
Randomization
Restriction
Matching
Stratification
Multivariate Techniques
Name a direct cause and indirect cause of a common cold
Direct: viral infection
Indirect: going to a party, poor hand hygiene
What type of trial is this?
Researchers want to examine whether adding iron to flour reduces risk of anemia in women. 400 women were enrolled in the study. 200 were randomly given fortified flour and the other 200 received non-fortified flour. The researchers measured anemia cases after 5 years.
Clinical Trial
What type of study is described below?
Researchers compare average obesity rates to average sugary drink consumption in all 50 states.
Ecologic
Researchers studied whether firefighters have an increased risk of developing respiratory disease. They monitored 100 firefighters and 100 non-firefighters for 10 years. 55 firefighters and 20 non-firefighters developed respiratory disease.
Calculate the etiologic fraction and interpret it.
Etiologic fraction = (Ie- Ine)/ Ie = (0.55 - 0.2) / 0.55 = 0.636
Ie = A / (A+B) = 0.55
Ine = C / (C+D) = 0.2
Being a firefighter accounts for 63.6% of respiratory disease in firefighters.