Week 124: Vaccination

Question 1

What is proportion?

Answer 1

number with disease/total number

Question 2

What is prevalence?

Answer 2

number with disease at any particular time/total number in population at that time

Question 3

What is risk/cumulative incidence?

Answer 3

number of new cases of disease in period/number initially free of disease

Question 4

What is incidence rate?

Answer 4

number of new cases of disease/(total number x total interval)

Question 5

What is difference in means between exposure groups?

Answer 5

mean in exposed - mean in unexposed

Question 6

What is population attributable risk?

Answer 6

overall risk - risk among unexposed

Question 7

What is the risk ratio?

Answer 7

risk in exposed individuals/risk in unexposed individuals

Question 8

What is the odds of disease?

Answer 8

number of individuals with the disease/number of individuals without the disease

Question 9

What is the odds ratio?

Answer 9

odds of disease in exposed individuals/odds of disease in unexposed individuals

or

odds of exposure in individuals with disease/odds of exposure in individuals without disease

Question 10

What is validity?

Answer 10

Accuracy

Question 11

What is reliability?

Answer 11

Precision

Question 12

What is confounding?

Answer 12

An association with a third variable that provides an alternate explanation for the observed association between exposure and disease

Question 13

What is the p value?

Answer 13

The probability that the difference between the groups would be as big or bigger than that observed, if the null hypothesis of no difference is true. The smaller the p value, the stronger the evidence against the null hypothesis of that there is no difference between the groups

Has a threshold of 0.05. P has to be smaller than this for there to be confidence in the results

Question 14

What is a null hypothesis?

Answer 14

The hypothesis that there is no difference between two groups

Question 15

What is a case series?

Answer 15

A report on an observed unusual occurrence of either a new disease or an association between exposure and disease

Question 16

What are ecological studies?

Answer 16

A study in which the unit of analysis is a group rather than an individual; instead of measuring exposure of individual and effect - look at average of something compared to average effect

Question 17

What is a cross-sectional study?

Answer 17

• Mainly used to measure the burden of disease in a population, though can also examine risk-factor associations
• Snapshot of disease in a population at a moment in time
• Has a target population

Question 18

What is a case-controlled study?

Answer 18

• Compares frequency of exposure among people with the disease (cases) with than in a comparable group without the disease (controls)
• Look at disease and attempt to find common exposure

Question 19

What is a cohort study?

Answer 19

• Observational studies in which the exposures of interest are measured at the start of the study, among people who have not yet developed the outcome
• Can have prospective or historical
• Look at impact of exposure

Question 20

What is the hierarchy of evidence?

Answer 20

• Case studies
• Ecological studies
• Cross-sectional study
• Case-control study
• Cohort study
• Randomised controlled trial
• Meta-analysis of randomised controlled trials

Question 21

What is sensitivity?

Answer 21

The proportion of those with the condition who have a positive test result

Question 22

What is specificity?

Answer 22

The proportion of those without the condition who have negative test results

Question 23

What is an alpha (or type 1) error?

Answer 23

Wrongly rejecting the null hypothesis

Question 24

What is a beta (or type 2) error?

Answer 24

Wrongly accepting the null hypothesis