Statistics Flashcards
(37 cards)
What is sensitivity?
Proportion of patients who have condition who have positive test result
How is sensitivity calculated?
True positive / true posoitive + false negative (all patients with condition)
What is specificity?
Proportion of patients without condition who have negative test result
How is specificity calculated?
True negative / true negayive + false positive (all patients without condition)
What is positive predictive value?
Chance patient has condition if diagnostic test is positive
How is positive predictive value calculated?
True positive / true positive + false positive
What is negative predictive value?
Chance patient does not have condition if diagnostic test is negative
How is negative predictive value calculated?
True negative / true negative + false negative
What is likelihood ratio for positive result?
How much odds of disease increase with positive test result
How is the likelihood ratio for a positive test result calculated?
Sensitivity / (1-specificity)
What is the likelihood ratio for a negative test result?
How much odds for a disease decrease with a negative test result
How is likelihood ratio for a negative test result calculated?
(1-sensitivity) / specificity
What is a null hypothesis?
States no difference between 2 groups
What is an alternate hypothesis?
States there is a difference between groups
What is a type 1 error when testing null hypothesis?
Null hypothesis is rejected when null hypothesis is actually true
(saying there’s a difference when there’s not)
What is the probability of making a type 1 error?
Alpha
What is a type 2 error when testing a null hypothesis?
Null hypothesis accepted when it is false
What is the probability of making a type 2 error?
Beta
What is the p value?
Assuming null hypothesis is true, p value is probability of obtaining a result by chance at least as extreme as one observed
What is the power of a study?
Probability of correctly rejecting null hypothesis when it is false
How is the power of a study calculated?
1 - beta (probability of making type 2 error )
What are the 2 types of significance tests?
Parametric tests - for quantitive data in normal disturbution (mean=median=mode)
Non parametric - if qualitative data or shewed distrubution
What are the types of parametric significance tests?
Student’s T test
Pearson product-moment coefficient - shows correlation
What are the types of non parametric tests?
Mann-Whitney U test
Wilcoxon signed rank test
chi-squared test
Spearman or Kendall rank
