Public health Flashcards
cross sectional study
- frequency of disease and frequency of risk-related factors are assessed in the present
- What is happening?
- measures prevalence and risk factor association
case-controlled study
- compares a group of people with disease to a group without
- looks to see if odds of exposure or risk factor differs
cross sectional study in my words
- takes a slice
- takes place at the present
- measures prevalence
case-controlled study in my words
- always in the past
- split by groups that do and don’t have disease
- looks for if something was a risk factor
- “if they have the disease, did something put them at risk”
cohort study in my words
- “if they have a risk, did they develop the disease”
- measure relative risk
- can be in the past or future
triple blind
blind to analysis of data
case-fatality rate
number of fatal cases / total number of cases
95% is how many SDs
1.98 (99% = 2.58)
standard error
- standard deviation of a number of sample means
- SD/ square root of n
confidence interval
- accounts for variability of sample means
- = mean +- z score + standard error
standard error takes into account what two factors
standard deviation and sample size (n)
hawthorne effect
- observer effect
- subjects change their behavior because they know they are in a study
Berkson’s bias
- specific selection bias created by choosing hospitalized patients as control group
lead-time bias
- using a screening method that detects a disease earlier, leading to an apparent prolongation of survival
- example: screening for PSA diagnoses prostate cancer earlier leading to longer survival times
Pygmalion effect
researchers belief in efficacy of treatment can change its actual effect
- example: if you think people are stupid, your intervention wont work as well
recall bias
- inaccurate recall of past exposures
- usually seen when asking questions
cumulative incidence
number of new cases of a disease / number of people at risk
- remember to subtract people that already have the disease because they are not at risk
power
the ability to detect between groups when one actually exsists
power equation
1-beta (type II error)
beta
study does not reject the null hypothesis when it should
ecological study
like a cross sectional study but it uses population data instead of individual data
effect modification
when the effect of an exposure on an outcome is modified by another variable
how effect modification differs from confounding
stratification is used to distinguish the difference. When the confounder is removed, there is no longer a difference between the two
attrition bias
when loss to follow up is greater for one group than another
selection bias
systemic difference between groups
misclassification bias
exposure and outcome are not measured properly, it affects both group equally
- example = nonfunctioning blood pressure cuff