Biostatistics

Question 1

Standard deviation

Answer 1

Variation of values w/in sample of population

Question 2

Standard error of mean

Answer 2

Variation of sample means from true population mean

Question 3

Confidence interval

Answer 3

CI = range [mean –Z (SEM)]: [mean + Z(SEM)]

90% CI Z = 1.645
95% CI Z = 1.96 (2)
99% CI Z = 2.57

Question 4

Risk or rate difference

Answer 4

RD = (risk/rate of exposed) – (risk/rate unexposed)

RD less than 0 = decreased risk
RD greater than 0 = increased risk
RD = 0 no difference

Question 5

Rate or risk ratio

Answer 5

RR= Re/Ru

Re > Ru = >1
Re less than Ru = less than 0
Re = Ru =1 Ho supported

If CI crosses 1, cannot reject Ho

Question 6

t-test

Answer 6

2 groups
continuous variables
eg weight

Question 7

ANOVA

Answer 7

3+ groups

continuous

Question 8

X2

Answer 8

Present or proportion of categorical outcomes in 2+ groups

Male vs female

Question 9

Correlation coefficient

Answer 9

+ 2 variables increase together
- 2 variables – one increases, one decreases

measure relationship of 2 variables

r=1 perfect correlation
r=0 no relationship

r>0 +
r less than 0 = -

Question 10

Coefficient of determination

Answer 10

R2 = goodness of fit
Study model regression
Line to data points