Stats

Question 1

How is SEM calculated?

Answer 1

Standard Deviation /
square root of ‘n’

n = sample size

Question 2

Calculate relative risk reduction

100 working women and 110 women who are house wives are followed up through pregnancy. 40 working women had LBW babies and 21 house wives had LBW babies.

Answer 2

Draw table
Top: Behaviour: working/housewife
Left side: Outcome: LBW Y/N

(40/100) / (21/110) = 2.1

2.1

CONTRAST odds ratio of LBW
(40/21) / (60/89) = 2.8

Question 3

What non-parametric tests can be used to test the induction of labour interval between normal and pre eclamptic women? Name 3

Answer 3

Non parametric is for Names or Not normally distributed

Mann Whitney
Wilcox Rank
Spearman

Question 4

How is the perinatal mortality rate defined?

Answer 4

The number of stillbirths and the number of neonatal deaths within 7 days of life, per 1000 births

Question 5

ABO blood grouping is?
Parametric/nonparametric
nominal/ordinal

Answer 5

Non-parametric nominal

Question 6

What is the risk of uterine rupture during a VBAC after 1 CS?

Answer 6

0.5%
or
1 in 200

Question 7

The diamond shape Forest graph, lateral angles represents:

Answer 7

95% CI

Question 8

What is the failure rate of vasectomy

Answer 8

0.5/1000

Question 9

Null hypothesis is ACCEPTED if
i.e. say the variable is without effect

Answer 9

p > 0.05

Question 10

Statistical analysis used for data with normal distribution. Name 3

Answer 10

Student t
Pearson (P for parametric)
ANOVA

Question 11

What is the data type of
‘moderate / mild / severe’

Answer 11

Ordinal

Question 12

What is an alpha or type 1 error
(with regards to the null hypothesis)

Answer 12

False positive
Incorrectly rejecting the null hypothesis

Question 13

What gestation is defined as stillbirth rather than miscarriage?

Answer 13

24 weeks

Question 14

Statistical heterogenicity means

Answer 14

Difference between studies

Question 15

Calculate maternal mortality ratio

Total number of live births 250,000, early neonatal death 1500, Maternal death 750.

Answer 15

Maternal mortality ratio =
(Maternal deaths /live births) X 100,000

(750/250,000) X 100,000 =
0.003 X 100,000 = 300

Question 16

Calculate SEM
For a group of 10,000
If the Mean 245 and SD 50.

Answer 16

SEM = SD/√n = 50/√10,000 = 50/100 = 0.5

Question 17

Which study design would describe the relationship between shoulder dystocia and neonatal birth weight ?

Answer 17

retrospective case-controlled study

Question 18

Calculation for negative predictive value

Answer 18

TN / TN + FN

Question 19

What is the mode?

Answer 19

The most frequently occurring number (fashionable!)

Question 20

Grade B recommendation of RCOG means

Answer 20

well controlled studies but non randomized

Question 21

Incidence of “RARE” disease when translated into mathematics is?

Answer 21

1:1000 or rarer

Question 22

Calculate BMI
150cm height and 90 kgs weight

Answer 22

BMI = weight / height in metres squared
90kg / 1.5 x 1.5
90/ 2.25 = 40

<18.5 underweight range.
<25, healthy weight range.
<30, overweight range.
Class 1 Obesity <35
Class 2 Obesity <40
*Class 3 Obesity 40 or higher

Question 23

Calculate perinatal mortality

Answer 23

stillbirths (>=24) and early neonatal (<7/7) deaths per thousand

(BUT question on paper from 2018 and WHO define perinatal period as from 22 weeks?)

Question 24

What represent the 2 axis of ROC curve ?

Answer 24

Sensitivity (vertical) over
1-specificity (horizontal)

Question 25

What do the bottom and top represent on the box-and-whisker plot?

Answer 25

Lower and upper quartile

Question 26

Odds ratio calculation Del <34/40 (total 209) Smokers 31 Non-smokers 178 Del >34/40 total 926 Smokers 58 Non-smokers 659

Answer 26

Behaviour: Smoking Outcome/risk: Del at <34/40/>34/40 (31/178) / (58 / 659) 17.42/8.8 = 1.98 So odds doesn't 'use' the total it's e.g. 1 in 9 (out of 10 total)

Question 27

NNT calculation

Answer 27

1 / ARR Absolute risk reduction ARR is % risk decrease from one group to another e.g. drug reduces chance of bad outcome from 50% to 40% then ARR = 10% or 0.1 1 / 0.1 = 10

Question 28

Pregnancy rate with COCP if perfectly compliant and non perfectly compliant

Answer 28

0.1 / 5-6

Question 29

VTE with COCP

Answer 29

6 / 10,000

Question 30

IUD Pregnancy. What is the risk of Ectopic Pregnancy

Answer 30

1/20

Question 31

The Probability of sarcomatous change occurring in fibroid is

Answer 31

0.1%

Question 32

Grade A RCOG recommendation means

Answer 32

At least one randomised controlled trial

Question 33

What type of variable is BMI ? ordinal / nominal / continuous / categorical / discrete

Answer 33

Continuous

Question 34

Incidence of uterine rupture in IUCD insertion

Answer 34

1/5000

Question 35

What is represented by the equation Sensitivity/(1-specificity)?

Answer 35

Positive likelihood ratio

Question 36

What is the correct formula to calculate specificity?

Answer 36

TN / TN + FP

Question 37

Calculate PPV

Answer 37

TP / TP+FP

Question 38

Calculate sensitivity

Answer 38

TP / TP + FN

Question 39

A study between soya milk and improvement of menopause symptom. the null hypothesis H0 should state that...

Answer 39

There is no relation/difference between soya milk intake and menopause symptoms

Question 40

WHO defines perinatal mortality as

Answer 40

number of still births after 22 wks & early neonatal deaths per 1000 births

Question 41

What kind of variable is 'gestational age'

Answer 41

interval named, ordered, with proportionate intervals between variables

Question 42

How do you calculate the type 2 error?

Answer 42

1 - power e.g. power is 90% 1 - 0.9 = 0.1 or 10%

Question 43

Risk of expulsion of IUD

Answer 43

~5% (google)

Question 44

Risk of ectopic pregnancy with IUD

Answer 44

<1 per 1000 years of use

Question 45

Risk of malignant transformation of leiomyoma into leiomyosarco

Answer 45

0.01%

Question 46

When a pregnant person is on carbamazepine and lamotrigine, what percent will have foetal congenital anomalies

Answer 46

>10%

Question 47

What is the leading cause of maternal death according to MBBRACE Overall direct indirect

Answer 47

Overall - Cardiac Thrombosis and thromboembolism is the leading direct cause of death during or up to six weeks after end of pregnancy. You clot because you are pregnant. Cardiac disease leading indirect cause of death You have cardiovascular disease before you are pregnant.

Question 48

What is the recurrence rate of ectopic pregnancy with a history of salpingectomy

Answer 48

15 - 20%

Question 49

What % of people with GDM go on to have T2DM

Answer 49

30-40% or more

Question 50

Calculate the interquartile range Number top 25% minus Number bottom 25% 2,3,4,5,6,6,6,7,7,8

Answer 50

7 - 4 = 3

Question 51

Calculation for the false negative rate

Answer 51

FN/FN+TP Or if sensitivity is 90% and specificity is 90% FNR is 10%

Question 52

Calculate the absolute risk reduction Placebo 50% risk New drug 40% risk

Answer 52

ARR absolute risk reduction of 10% or 0.1

Question 53

What is the % of BP injury in cases of shoulder dystocia

Answer 53

16%

Question 54

Rhesus negative incidence in uk

Answer 54

16%

Question 55

When does the Odds ratio approximate risk ratio?

Answer 55

When the disease studied is rare

Question 56

What kind of data does a histogram present

Answer 56

Continuous

Question 57

What is the % risk of recurrent preeclampsia?

Answer 57

20%