Exam #1: Biostatistics V

Question 1

What is a proportion?

Answer 1

of observations/ whole

*****Note that this is the same things as the probability

Question 2

What is a rate? How does this relate to a proportion?

Answer 2

• Rates are similar to proportions except a multiplier is used
• Rates have a time reference i.e. are calculated over a period of time

Question 3

What are vital statistics?

Answer 3

Demographic statistics that describe the health of a population

Question 4

What are the most widely used vital statistics?

Answer 4

• Mortality rates

- Morbidity rates

Question 5

What is a crude mortality rate?

Answer 5

of all deaths in a region, in a given year/ total population in that region/ year

Question 6

What is a specific mortality rate?

Answer 6

This relates to a specific population death rate e.g. women, men…etc.

Question 7

What is a morbidity rate?

Answer 7

individuals who develop a disease in a period of time/ region/ total

Question 8

What does the morbidity rate define?

Answer 8

Prevalence or prevalence rate

Question 9

What is the difference between prevalence and incidence?

Answer 9

Prevalence= # cases/ region/ time

Incidence= # of NEW cases

Question 10

Why are morbidity and mortality rates adjusted?

Answer 10

There may be confounding factors in a population

*****E.g. mortality rate as a measure of health in a very old population should be corrected for

Question 11

What is the experimental event rate (EER)?

Answer 11

How often an event occurs within the experimental group (non-control group) of an experiment

Question 12

What is the formula for calculating an EER?

Answer 12

A/ A + B

Question 13

What is the control event rate (CER)?

Answer 13

How often an event occurs within the control group of an experiment

Question 14

What is the formula for calculating a CER?

Answer 14

C/ C + D

Question 15

What does absulate risk reduction (ARR) mean?

Answer 15

Change in risk of a given activity or treatment in relation to a control activity or treatme

Question 16

What is the formula for calculating the ARR?

Answer 16

EER - CER

Question 17

What is the NNT?

Answer 17

Number of patients who need to be treated to prevent one additional bad outcome

Question 18

How do you calculate the NNT?

Answer 18

NNT= 1/ARR i.e.

NNT= 1/ (EER - CER)

Question 19

What is the relative risk reduction?

Answer 19

Amount of risk reduction relative to the baseline risk

Question 20

What is the formula for the relative risk reduction?

Answer 20

(EER - CER)/ CER

OR

A/ (A+B) / C/ (C+D)

Question 21

What is relative risk?

Answer 21

Ratio of incidence of disease in people exposed to risk factor vs. incidence in people without risk factor

Question 22

What is the odds ratio?

Answer 22

Odds that a person with disease is exposed to a risk factor vs. odds of a person without the disease exposed to the same factor

Question 23

What types of studies use relative risk and odds ratio?

Answer 23

Relative risk= cohort

Odds ratio= case-control

Question 24

What does a RR or OR that is

Answer 24

Protective exposure

Question 25

What does a RR or OR that is >1 mean?

Answer 25

Risky exposure

Question 26

What does a RR or OR =1 mean?

Answer 26

No effect of exposure

Question 27

Do the distributions of RR or OR follow the theoretical probability distribution?

Answer 27

No

Question 28

How can you transform RR or OR to follow a normal distribution?

Answer 28

Take the natural log of RR or OR

Question 29

Calculate EER, CER, ARR, NNT, RRR, RR, and OR in the example provided in the ppt. Interpret the results of the RR and OR.

Answer 29

N/A