Statistic Definitions Flashcards
What is the definition and formula for sensitivity?
probability that test results will be positive in patients with disease; (rules in)
sensitivity = TP / (TP + FN) [true positive/all that have disease]
sensitive tests are useful for screening since they are unlikely to miss a patient with disease
What is the definition and formula for specificity?
probability test result will be negative in patients without disease; (rules out)
specificity = TN / (FP + TN) [true neg/all that dont have disease]
specific tests are useful for confirmation as they don’t result in treatment of an unaffected individual
What is the definition and formula for positive predictive value?
probability patient with a positive test actually has the disease;
PPV = TP / (TP + FP)
What is the definition and formula for negative predictive value?
probability patient with a negative test actually has no disease;
NPV= TN/(FN+TN)
What is the difference btw incidence and prevalence?
Incidence- Number of newly reported cases of a disease during a given time period
Prevalance- Total number of cases of a disease present in a location at any time point
What is the definition of relative risk?
risk of developing disease for people with known exposure compared to risk of developing disease without exposure; obtained from cohort studies
when RR>1 the incidence of the outcome is greater in the exposed/treated group
The power of a study takes into account the probability of what type of error?
Type II or beta error
Power= 1-beta
One falsely concludes that there is no significant association when there actually is an association (resulting in a false-negative study that rejects a true alternative hypothesis)
What is the definition of a Type I or alpha error?
Null hypothesis is rejected that is true
false positive study; difference found when there isnt a difference
What is the definition of a Type II or beta error?
Null hypothesis is accepted that is false
false negative study; no difference found when there actually exists a difference
A post-hoc statistical correction made to P values when several dependent or independent statistical tests are being performed simultaneously on a single data set describes what?
Bonferroni correction
The estimated range of values which likely includes the unknown parameter under investigation is defined as?
Confidence interval
The paired Student’s t-test is most appropriately used for which of the following?
Compare two observed means in matched groups
A Chi-square test is appropriate for?
Comparison of two or more groups of categorical (non-numerical data/proportions);
Fischer exact test used if groups are small
What test is used to assess for publication bias in a meta-analysis?
Funnel plot
