Biostats Flashcards
Relative risk formula
risk in tx group / risk in control group
In this type of distribution, the mean, median, and mode are the same value.
normal
retrospective comparisons of cases (patients with a disease) and controls (patients without the disease)
case control study
retrospective or prospective comparisons of patients with an exposure to those without an exposure
cohort study
Which of the following statements are true regarding the p-value?
a. If the alpha in a study is 0.01, p < 0.05 indicates the result is statistically significant.
b. It represents the level of clinical significance.
c. A study result is considered statistically significant if the p-value is less than alpha.
d. It provides info for rejecting or not rejecting the null hypothesis.
e. It can be set to any number by the investigator and be clinically relevant.
c, d
NNT formula
1 / (risk in control group - risk in tx group)
(% risk in control group) - (% risk in tx group)
absolute risk reduction
describes how effectively a test identifies patients with the condition
sensitivity
describes how effectively a test identifies patients without the condition
specificity
This type of analysis can be used to compare programs with similar or unrelated outcomes, as long as the outcome measures can be converted to dollars.
cost-benefit
Rank the studies from most reliable to least reliable:
Case control studies
Randomized controlled trials
Meta-analyses
Cohort studies
Case series
Meta-analyses, randomized controlled trials, cohort studies, case control studies, case series
This type of study combines data from different, but related studies, in order to increase the power of the study.
meta-analysis
What kind of error occurs when the alternative hypothesis is accepted and the null hypothesis is rejected in error?
type 1
What kind of error occurs when the null hypothesis is accepted when it should have been rejected?
type 2
represents the spread (or variability) of data from the mean when data is normally distributed
standard deviation
this type of analysis is used to compare the clinical effects of 2 or more interventions to the retrospective costs
cost-effectiveness
A study comparing drug A to placebo determined that the relative risk reduction in all-cause mortality was 0.33. Which of the following statements is correct?
a. Patients who received drug A were 67% less likely to die compared to patients in the placebo group
b. Patients who received drug A were 33% as likely to die as patients in the placebo group
c. For every 100 patients who received drug A, 33 fewer died compared to patients in the placebo group
d. Patients who received drug A were 33% less likely to die compared to patients in the placebo group
e. 33 patients needed to be treated with drug A to prevent one death
d
Includes data for all patients originally allocated to each treatment group (active and control) even if the patient did not complete the trial according to the study protocol (e.g., due to non-compliance, protocol violations or study withdrawal).
intention-to-treat analysis
conducted for the subset of the trial population who completed the study according to the protocol (or at least without any major protocol violations)
per protocol analysis
hazard ratio formula
(hazard rate of tx group) / (hazard rate of control group)
In a clinical trial, what do the independent variables include?
intervention (drug, dose, frequency), comparator arm (placebo, active drug), and inclusion criteria
implies no difference in risk of the outcome between the groups
RR = 1
implies greater risk of the outcome in the treatment group
RR > 1
implies lower risk of the outcome in the treatment group
RR < 1
If a study with metoprolol had a RR of 57%, what is the correct interpretation?
a. Patients that received metoprolol were 57% less likely to have progression of disease as placebo-treated patients.
b. Patients that received metoprolol were 57% as likely to have progression of disease as placebo-treated patients.
b
used for continuous data when the study has 2 independent samples
student t-test
used to test for statistical significance when using continuous data with 3 or more samples, or groups
ANOVA
for nominal or ordinal data, this test is used to determine statistical significance between treatment groups
chi square test
