CPH EXAM Definitions Simplified Study Exam With Accurate Answer.

Attributable risk - correct answer Rate of disease in exposed individuals that can be attributed to the exposure. Or the proportion of all cases that can be attributed to a particular exposure. Adjusted rate - correct answer Effects of differences in composition of pops being compared have been minimized by statistical methods. ex: regression analysis and strandardization -often used on rates or relative risks Ecological Fallacy - correct answer Bias that may occur because an association observed between variables or an aggregate level does not represent the association that exists at an individual level Confidence Interval - correct answer 95% confident that the true value of a variable is contained within the interval. -used to account for sampling variability -it is a point estimate +_ margin of error, where the point estimate is the best estimate of teh unknown parameter and the margin of error is the product of the confidence level and the standard error. if a 95% CI for the differences in mean does not include 0 (the null value) then there is eveidence of a statistically significant difference at sigma=0.05 Clinical Trial Phases - correct answer 1. Safety and Pharmacologic profiles 2. pilot efficacy studies 3. extensive clinical trials 4. after the FDA approves, look at specific effects to establish incidence of adverse reactions, etc. longterm use effects. interpretation of studies - correct answer temporality: cause precedes effect Specificity: important in assessing the possibility of biases. Consistency: several studies showing similar results. homogeneity statistically. Confounders - correct answer -non-causal association between exposure and outcome as a result of a third variable. -distortion of effect by other factors -must be related to exposure AND outcome -not an intermediate variable on causal pathway Controlling for confounders - correct answer before data collection: random collection, individual matching, frequency matching After data collection: direct adjustment, indirect adjustment, mantel-haenszel, regression techniques Quality Assurance vs. Quality Control - correct answer QA: ensure quality before data collection QC: monitor and maintain quality during study reliability vs. validity - correct answer R: precision, reproducibility V: accuracy, absence of bias systematic error - correct answer (lack of validity) if there's a difference between what is actually being estimated and what is intended to be measured. Increasing sample size doesn't help. Random Error - correct answer (lack of precision) occurs, but increasing sample size helps. RCT studies - correct answer Tests efficacy or effectiveness of healthcare services. random allocation of participants to different treatments. Includes blinding, placebo. gold standard for evidence. Community Intervention/cluster RCT - correct answer community-wide basis or groupwide Case-Crossover RCT design - correct answer -cases serve as their own control -exposure has transient effect Cross Sectional Studies - correct answer SNAPSHOT! at a single point in time. tells the prevalence and association. causation cannot be implied. a study that examines the relationship between diseases and other variables as they exist in a defined population at one particular time. Matching - correct answer used to make cases and controls as similar as possible to avoid confounding. ex: race, gender, age. +Maybe the only way to control confounding. increases statistical power, straightforward. -requires use of special analytical techniques, residual confounding can occur if you match continuous variables by category. types of matching - correct answer individual matching: case and control matched individually frequency matching: a group of controls Minimum Euclidean Distance measure: match to closest person. Cohort Studies - correct answer RISK RATIO, RELATIVE RISK, INCIDENCE RATE, RATE RATIO -rare exposures -group of subjects who shared experiences during a particular time. Determines if incidence is related to exposure. Concurrent/longitudinal cohort studies - correct answer starts now (with a baseline exam) and goes into future. expensive and time intensive. non-concurrent/retrospective cohort studies - correct answer assembled in past based on existing records. faster and quicker, but records can be limited or biased. follow up can be hard. Prevalence of disease - correct answer measure of the burden of disease in a community (new and existing cases). the number of events in a given population at a designated time. -obscures causal relationships