Statistics Flashcards
state the calculation for power in a study
power = 1 - probability of type II error
type II error is when the study does not reject H0
what is the equation used to calculate sensitivity
true positives / (false negatives + true positives)
what is the equation used to calculate specificity
true negatives / (true negatives + false positives)
what is the equation used to calculate positive predictive value
true positives / (true positives + false positives)
what is the equation used to calculate negative predictive value
true negatives / (true negatives + false negatives)
what is the equation used to calculate likelihood ratio for a positive result
sensitivity / (1 - specificity)
what is the equation used to calculate likelihood ratio for a negative result
(1- sensitivity) / specificity
how do you calculate number needed to treat (NNT)?
1 / absolute risk reduction
absolute risk reduction = experimental event rate (EER) - control event rate (CER)
how do you calculate relative risk reduction>
(EER - CER) / CER
state the coefficients used for
- parametric data
- non-parametric data
- parametric (normally distributed): Pearson’s coefficient
- non-parametric: Spearman’s coefficient
describe the following non-parametric tests
- Mann Whitney U test
- Wilcoxon signed-rank test
- Chi-squared test
- Mann Whitney U test
> compares ordinal, interval or ratio scales of unpaired data - Wilcoxon signed-rank test
> compares two sets of observations on a single sample e.g. before after test on same population following an intervention - Chi-squared test
> used to compare proportions or percentages e.g. compares the % of patients who improved following two different interventions
*paired dats is obtained from a single group of patients, unpaired data is obtained from two different groups of patients