Stats & research

Question 1

case control

Answer 1

case-control

• observational, retrospective
• take condition (often rare) and matched control
• look back for exposure to certain thing
• give odds ratio

Question 2

cohort

Answer 2

cohort

• observational, prospective
• follow cases (w/ certain exposure) vs controls and look for development of problems
• give relative risk

Question 3

sensitivity and specificity

Answer 3

spec: true neg/ not got
- high specificity helps rule in

sens: true pos/ have got
- high sensitivity helps rule out

Question 4

absolute risk reduction

Answer 4

(rate of event in controls) - (rate of event in group)

Number needed to treat =1 / ARR

Question 5

funnel plots

Answer 5

show publication bias in meta analysis

Question 6

cross sectional survey

Answer 6

snapshot of clinical scenario

low statistical value

Question 7

odds ratio

Answer 7

if 80 people take drug 40 get better

odds of positive outcome is 1 (40/40)

if 100 were control placebo and 25 got better
odds is 25/75=0.33

odds ratio is 1/0.33=3

Question 8

power and p value

Answer 8

power= 1 - prob of type 2 error

p value = chance of type 1 error

type two say null is true when not (false neg)
type one say null is false when its true (false pos)

Question 9

comparison tests

Answer 9

parametric

• students t test
• pearsons - correlation

non-parametric

• chi squared - percentage
• man whitney - unpaired data
• wilcoxon - 2 obs on same set

Question 10

error type 1 and 2

Answer 10

T1 : null rejected but true (p value is chance of this)
T2: null accepted but not true

null hypothesis is that there is no relationship between 2 measured phenomena

1-(T2) = power

Question 11

standard deviation

Answer 11

root of variance

68. 3% w/in 1sd
69. 4 - 2sd
70. 7 - 3sd

95% within 1.96sd