16 June Epidemiology and Biostats Flashcards
Describe a cross-sectional study
Used to assess prevalence
Collects information at a specific point in time
Information about an entire population to look for risk factors and possible causes
It is a descriptive study and is observational not longitudinal or experimental
Seeks to answer: What is happening?
Can help identify prevalence and odds ratios
How is a cross-sectional study different from a case-control and a longitudinal study?
Cross-sectional looks at an entire population whereas a case-control study looks at a specific group of people with a given characteristic
Cross-sectional looks at one data point at one point in time whereas a longitudinal study looks at multiple data points repeatedly over a longer period of time
Describe a case control study
Compares people with disease to those without in an effort to determine what happened.
Helps establish odds ratio by looking for prior exposure or risk factor.
From now looking backwards
Describe a cohort study
Compares a group with a given exposure or risk factor to a group without these factors to see if factor affects likelihood of developing disease.
Looks for relative risk to determine who will likely get the disease.
From now looking forwards
Describe phase I of drug trials
Healthy volunteers establish whether or not the drug is safe and assess pharmacodynamic traits
Describe phase II of drug trials
Patients with the disease test whether or not the drug works and what the dosing should be
Describe phase III of drug trials
Large study with many patients randomly assigned to groups to assess whether the new treatment is as good or better than the current standard
Describe phase IV of drug trials
After the drug is approved for use, it is monitored for long-term and unseen effects to determine whether or not the drug can stay in use.
What phase of drug trials assesses the long-term effects of the drug and looks to see if it can stay on the market?
Phase IV
What phase of drug trials is on healthy volunteers to see if the drug is safe and to study the pharmacodynamics?
Phase I
What phase of drug trials is on a large group of patients assigned to several groups where the drug is compared to the effectiveness of the current standard to see if it is the same or better?
Phase III
What phase of drug trials is on a small group of patients with the disease to see if the drug works at all and to establish dosing and look for adverse side effects?
Phase II
What kind of observational study looks at patients with a disease to figure out what risk factors they might have in common to help determine what happened?
Case-control study
What kind of observational study looks at people with certain risk factors and follows them to see who gets the disease to help establish who will get a disease?
Cohort study
What kind of observational study is used to establish relative risk?
Cohort study
What kind of observational study is used to establish odds ratio?
Case-control study
What are two observational study types used to understand heritability and influence of environmental factors of a disease?
Twin concordance and adoption studies
What properties of a test are fixed and which are variable depending on disease prevalence?
Sensitivity and specificity are fixed and PPV and NPV vary depending on disease prevalence
How do PPV and NPV vary with pretest probability?
PPV varies directly with pretest probability
NPV varies inversely with pretest probability
How does the relationship between prevalence and incidence change based on the duration of a disease?
In a short-lived disease, prevalence and incidence are about equal
In a chronic disease, prevalence is much larger than incidence
Define absolute risk reduction
Take the percent of people without an intervention who develop a disease and subtract the percent of people with the intervention who have the disease to find the difference in percentage between the two groups
Define number needed to treat
NNT is the inverse of the absolute risk reduction
Define attributable risk
The difference between percentages of those exposed who developed disease minus those not exposed who developed the disease
Define number needed to harm
The inverse of attributable risk
What is confounding bias?
A factor is related to both the exposure and the outcome, but is not on the causal pathway.
Example: coal miners have higher rates of pulmonary disease than general population, but they also have a higher rate of smoking which is the actual cause of the increased prevalence of lung disease.
Describe mean, median, mode and the effect outliers have on them
Mean is the average and is most affected by outliers
Median is the middle value and is the average of the two middle values in an even set
Mode is the most common value and is the least affected by outliers
What is a type I and type II error in an experiment?
Type I: false-positive result, you thought there was a difference when there really was not one
Type II: false-negative result, you thought there was not a difference when in fact there was one
When is a t-test used?
Checks the differences between means of 2 groups
Remember that tea is meant for 2
When is an ANOVA used?
Checks differences between means of 3 or more groups
Stands for analysis of variance (has 3 words)
When is a Chi-square test used?
Checks differences between 2 or more percentages or proportions of categorical outcomes
Pronounce Chi-tegorical
