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Flashcards in Critical Appraisal and Statistics Deck (13):
1

Define the mean, mode and median

– Mean is the average
– Median is the “middle” number(s)
– Mode is the most frequent number

2

Define variance

– “averaged (squared) distance of data from the center”
– The sum, from 1 to n, of (xi – x)2 / (n-1)

3

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

4

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

5

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

6

How do you calculate sensitivity? What does it mean?
(use letters re: 2x2 table)

a/(a+c)

rule in

7

How do you calculate specificity? What does it mean?
(use letters re: 2x2 table)

d/(b+d)

rule out

8

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

9

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.

10

What is probability?

It is essentially the same thing as prevalence or chance.
= total with disease in question over the population

11

What is the odds?

It considers the chances for vs the chances against.
Calculate it by
probability/ (1-probability)

12

How do you calculate the odds ratio?

OR = Odds at risk/ Odds not at risk

13

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 -) = ________