Biostats Flashcards
Cross-sectional study
snapshot of a population
frequency of a disease and frequency of risk-related factors are assessed in the present
Measures prevalence
Case-control study
compares a group of people with disease to a group without disease
Measures odds ratio
Cohort study
compares a group with a given exposure or risk factor to a group without such exposure
Measures relative risk
What is the formula for sensitivity?
a/a+c
What is the formula for specificity?
d/b+d
What is the formula for PPV?
a/a+b
What is the formula for NPV?
d/c+d
What is the formula for odds ratio?
(a/b)/(c/d)
What is the formula for relative risk?
(a/a+b)/(c/c+d)
What is the formula for attributable risk?
(a/a+b) - (c/c+d)
What is the formula for absolute risk reduction?
ARR = (c/c+d) - (a/a+b)
What is the formula for NNT?
1/ARR
What is the formula for NNH?
1/AR
What is the formula for relative risk reduction?
RRR = 1 - RR
What is the formula for incidence?
incidence rate = # of new cases/# of people at risk
What is the formula for prevalence?
prevalence = # of existing cases/total # of people in population
Study X shows that VitC can prevent coronavirus infections, but 10 other studies show no benefit. What type of error is found in study X?
type 1 error (alpha error); false positive
Study Y shows that aspirin administration during an MI offers no improvement in patient morbidity or mortality. What type of error is present?
Type II error (beta error); false negative
What are the differences between mean, median, and mode?
mean = average median = middle mode = most common result
What does it mean to say that a statistical distribution has a positive skew?
positive skew = bigger tail to right side of graph, but graph (hump) is shifted left
mean > median > mode
What is attributable risk percent?
ARP = measure of the impact of a risk factor ARP = 100 x [(risk in exposed-risk in unexposed)/risk in exposed]
