Critical Appraisal and Statistics Flashcards
Define the mean, mode and median
– Mean is the average
– Median is the “middle” number(s)
– Mode is the most frequent number
Define variance
– “averaged (squared) distance of data from the center”
– The sum, from 1 to n, of (xi – x)2 / (n-1)
What is standard deviation and how do you calculate it?
– a quantity calculated to indicate the extent of deviation for a group as a whole
– The square root of the variance
What is the standard error of the mean and how do you calculate it?
– changes with sample sizes, gets more accurate as our data sample gets bigger
– The standard deviation divided by the square root of n
Define a p-value
the probability of an observed (or extreme) result arising just by chance
it is not synonymous with significance, of more importance is the confidence interval and effect size
How do you calculate sensitivity? What does it mean?
use letters re: 2x2 table
a/(a+c)
rule in
How do you calculate specificity? What does it mean?
use letters re: 2x2 table
d/(b+d)
rule out
How do you calculate positive predictive value? What does it mean?
(use letters re: 2x2 table)
a/ (a+b)
Positive predictive value is the probability that subjects with a positive screening test truly have the disease
How do you calculate negative predictive value? What does it mean?
(use letters re: 2x2 table)
d/(c+d)
Negative predictive value is the probability that subjects with a negative screening test truly don’t have the disease.
What is probability?
It is essentially the same thing as prevalence or chance.
= total with disease in question over the population
What is the odds?
It considers the chances for vs the chances against.
Calculate it by
probability/ (1-probability)
How do you calculate the odds ratio?
OR = Odds at risk/ Odds not at risk
What is the relative risk
- it looks at the probability of an event among those that are risk + vs those that are risk -
- P (appy in FHx +) / P (appy in FHx -) = ________
What are 5 components when obtaining informed consent in participation in a research project?
Free choice Complete information, understandable Confidentiality Assent Consent by minors
