Statistics

Question 1

what is incidence of disease?

Answer 1

number of new cases of disease/number of people at risk

Question 2

what is sensitivity in a test?

Answer 2

ability of the test to detect every case of the disease

Question 3

what is specificity in a test?

Answer 3

ability of the test to exclude healthy non diseased people

Question 4

what is PPV vs NPV?

Answer 4

PPV is probability of having the disease if the test if positive

NPV probability of being disease free if test if negative

Question 5

what is selection bias?

Answer 5

issue with selection process of sample

Question 6

what is measurement bias?

Answer 6

data gathering process can distort information

Question 7

what is confounding bias?

Answer 7

characteristic associated with factor being studied that cannot be separated from the factor being studied

Question 8

what is recall bias?

Answer 8

subjects cannot recall events

Question 9

what is experimenter expectancy bias?

Answer 9

what the investigator expects is communicated and alters the info

Question 10

what is late look bias?

Answer 10

info collected late so most severe cases are less likely to be found e.g due to death

Question 11

what is the N in a case report?

Answer 11

N=1

Question 12

how are results of cross sectional studies analysied?

Answer 12

Chi square

Question 13

what is a case control study? how is data presented?

Answer 13

diseased compared with disease free

results expressed via an odds ratio

Question 14

how are results of cohort studies expressed?

Answer 14

relative vs absolute risks

Question 15

what are experimental study designs?

Answer 15

RCT
double blind RCT
crossover study

Question 16

how to calculate range?

Answer 16

subtracts smallest from largest

Question 17

what does a low SD mean?

Answer 17

data points are close to the average

Question 18

what is SEM?

Answer 18

standard error of the mean

how well the mean estimates the mean of the population

Question 19

what is a confidence interval?

Answer 19

provides a measure of uncertainty around an estimate based on a sample

Question 20

what is a p value?

Answer 20

probability of obtaining a test statistic as extreme as the one observed

Question 20

what does it mean if CI does not include a range with 1.0 in it?

Answer 20

significant difference in risk

Question 21

standard p value?

Answer 21

0.05 (5%)

Question 22

what does a meta analysis do?

Answer 22

synthesis of results of different studies to obtain a single p value

Question 23

what is the best study for assessing an intervention?

Answer 23

RCT

Question 24

what is the best study for assessing diagnostic tests?

Answer 24

cross sectionals tudy

Question 25

what is the best study for assessing prognosis?

Answer 25

cohort study

Question 26

what is a type 1 statistical error?

Answer 26

false positive incorrectly rejecting a true null hypothesis

Question 27

what is a type 2 statistical error?

Answer 27

false negative incorrectly accepting a true null hypothesis

Question 28

parametric vs non parametric test?

Answer 28

parametric - assume a normal distribution of the variable being tested e.g Pearson non parametric - non normal distribution of the variable being tested e.g Spearman

Question 29

what is a maternal death defined as?

Answer 29

death of a woman who is pregnant or within 42 days of pregnancy

Question 30

rate of ectopic pregnancy?

Answer 30

1 in 90

Question 31

risk of hypoxic ischaemic encephalopathy in a VBAC?

Answer 31

8 in 10,000

Question 32

risk of uterine rupture in a VBAC?

Answer 32

22-74 in 10,000

Question 33

risk of additional birth related perinatal death in a VBAC?

Answer 33

2-3 in 10,000

Question 34

what can decrease type 2 errors?

Answer 34

increasing sample size

Question 35

what can reduce risk of ovarian cancer?

Answer 35

Oral contraceptive use Higher Parity Breast feeding Hysterectomy Tubal Ligation Statins SLE

Question 36

what is the maternal mortality ratio?

Answer 36

number of maternal deaths per 100,000 live births

Question 37

axis of a ROC curve?

Answer 37

x - 1-Specificty y - sensitivity

Question 38

what is perinatal mortality rate?

Answer 38

the number of stillbirths and deaths in the first week of life per 1000 births