Lecture 9 - Review

Question 1

What is incidence?

Answer 1

Number of new cases of disease in a population over a period of time

Question 2

What is prevalence?

Answer 2

Total number of people who have a particular disease or attribute over a specified period of time

Question 3

Is case-control studies retrospective or prospective?

Answer 3

Retrospective
(Start with the case then work backwards to see if they had exposure)

Question 4

What are some feartures of high quality stduueoos?

Answer 4

Large sample size
Prospective studies
Blinded
Random allocation of subjects to groups
Control group
Low loss to follow up

Question 5

What is confounding?

Answer 5

External environmental variables which are independently associated with the exposuuure and the outcome but are not in the causal pathway

Question 6

What is bias?

Answer 6

Systematic error in an epidemiological study that results in an incorrect estimate of the association between the exposure and the condition

Question 7

How does the timing of case-control and cohort studies differ?

Answer 7

Case-control = retrospective
Cohort = prospective

Question 8

How does the timing of case-control and cohort studies differ?

Answer 8

Case-control = retrospective
Cohort = prospective

Question 9

How do case-control and cohort studies differ in terms of rare diseases?

Answer 9

Case-control = good for rare diseases

Cohort = good for rare exposure

Question 10

How do case-control and cohort studies differ in terms of calculating incidence?

Answer 10

Case control = cannot calculate incidence

Cohort = can calculate incidence

Question 11

How do case-control and cohort studies differ in terms of risk of bias?

Answer 11

Case control = risk of recall bias

Cohort = less risk of bbias

Question 12

What is the positive predicted value?

Answer 12

Proportion of people with a positive test result that actually have the condition

You test positive, what are the chances you actually are positive

Question 13

What is the negative predicted value?

Answer 13

Proportion of people with a negative test result that do not have the condition

You test negative, what are thee chances you actually are negative

Question 14

What is sensitivity?

Answer 14

How good a test is at detecting the specific condition (So the TRUE POSITIVE RESULT)

So you have the condition, what is the chance the test says you have it

Question 15

What is specificity?

Answer 15

How good a test is at only detecting the specifc condition (so TRUE NEGATIVE RESULT)

You are negative for the condition, what is the chances that the test says you are negative

Question 16

What is risk ratio?

Answer 16

Risk of disease in the exposed/risk of disease in the unexposed

Question 17

What type fo study are risk ratios used in?

Answer 17

Cohort studies

Question 18

What is odds ratio?

Answer 18

Disease in the exposed/ disease in unexposed

Question 19

What studies are odds ratios used in?

Answer 19

Case-control studies

Question 20

What studies are odds ratios used in?

Answer 20

Case-control studies

Question 21

What is meant by p<0.05?

Answer 21

Paper is 95% confident that the risk ratio lies in between the confidence interval

Question 22

What is the null value for risk ratios?

Answer 22

1

Question 23

What is the significance of p<0.05 and the value 1 is not in the 95% confidence interval?

Answer 23

We can reject the null hypothesis so the data is statistically significant

Question 24

Look at slide 14 , then the confidence interval, is this statistically significant?

Answer 24

The value 1 lies outside of the confidence interval, with 95% certainty we can reject the null hypothetical and women aged 18-45 are at a 2.5x greater risk of DVT over 5 years if they take the COCP compared to those who dont

Question 25

Comment on, reducing risk of MU in patients

RR - 0.32 0.17 - 0.79 (p<0.05)

Answer 25

The results are statistically significant since theres the null value of 1 is not within the 95% confidence interval and p<0.05 so Atorvastatin reduces risk of MI in patients witht high cholesterol by 68%