Biostats

Question 1

sensitivity

Answer 1

TP/(TP+FN)

Question 2

specificity

Answer 2

TN/ (TN+FP)

Question 3

PPV

Answer 3

TP / (TP+FP)

Question 4

NPV

Answer 4

TN / (TN+FN)

Question 5

incidence vs. prevalence vs. attack rate

Answer 5

incidence = # new cases/ # vulnerable
prevalence = #existing cases/population at risk
attack rate = #sick/ #who were exposed

Question 6

OR

Answer 6

(a/c)/(b/d) = ad/bc

Question 7

RR

Answer 7

(a/(a+b)) / (c/(c+d))

Question 8

relative risk reduction

Answer 8

1 - RR

Question 9

attributable risk

Answer 9

AR = a/(a+b) - c/(c+d)

Question 10

Absolute risk reduction

Answer 10

difference in risk compared to control

Question 11

NNT

Answer 11

1 / ARR

Question 12

number needed to harm

Answer 12

1 / AR

Question 13

random error

Answer 13

reduces the precision in a test

Question 14

systematic error

Answer 14

reduces the accuracy of a test

Question 15

examples of selection bias

Answer 15

• berkson bias (study only looking at inpatients), loss to follow up, health care worker study

Question 16

measurement bias

Answer 16

Hawthorne effect - pts who know they are being studied behave differently than they normally would

Question 17

positive skew data

Answer 17

mean > median > mode

- curve leans to the left (tail goes positive)

Question 18

negative skew data

Answer 18

mean < median < mode

- curve leans to the right (tail goes negative)

Question 19

type I error (a)

Answer 19

• stating that there is an effect or difference when there isn’t one
• a is the probability of making a type 1 error, if p <0.05 then there is a less than 5% chance that the data will show something that is not really there

Question 20

type II error (b)

Answer 20

• stating that there is not an effect or difference when one exists
• b is the probability of making a type II error
• 1-b is the statistical power, which is the probability of rejecting the null hypothesis when it is false (aka probability of finding a true relationship)
• increased power and decreased b by increasing sample size, increasing expected effect size and increasing precision of measurement

Question 21

calculating 95% confidence interval

Answer 21

• 95% CI = Mean +/- 1.96*SD/sqrt n

Question 22

t test

Answer 22

checks differences between the means of 2 groups

Question 23

ANOVA

Answer 23

checks differences between means of 3 or more groups

Question 24

chi-square test

Answer 24

checks differences between 2 or more percentages or proportions of categorical outcomes (not mean values)

Question 25

pincer grasp

Answer 25

10 months

Question 26

babinski disappears

Answer 26

12 months

Question 27

points to objects

Answer 27

12 months

Question 28

stranger anxiety

Answer 28

6 months

Question 29

separation anxiety

Answer 29

9 months

Question 30

object permanence

Answer 30

9 months

Question 31

first words

Answer 31

10 months

Question 32

number of cubes they can stack

Answer 32

age in years x 3

Question 33

feeds self with fork/spoon

Answer 33

20 months

Question 34

kicks ball

Answer 34

2 years

Question 35

200 words

Answer 35

2 years

Question 36

1000 words

Answer 36

3 years

Question 37

line, circle or stick figure

Answer 37

4 years

Question 38

hops on one foot

Answer 38

4 years

Question 39

grooms self/buttons buttons

Answer 39

5 years

Question 40

cooperative play

Answer 40

4 years

Question 41

tells detailed stories

Answer 41

4 years