Quiz 2

Question 1

Organizing Data: Line Listing

What is line listing used for?

lecture 5

Answer 1

used in routine surveillance, investigating an outbreak, conducting a study, etc. to compile information in an organized manner

organized like a spreadsheet with rows and columns

Question 2

Organizing Data: Line Listing

What makes up a line listing?

lecture 5

Answer 2

row: called a record or observation
- represents one person or case of disease

column: called a variable
- contains information about one characteristic of the individuals (race or date of birth)

Question 3

Organizing Data: Line Listing

What is a value?

lecture 5

Answer 3

value of a variable is the number or descriptor that applies to a particular person (5’6”, female, never vaccinated, etc.)

• the type of values influence the way in which the variables can be summarized

can be numeric but also can be descriptive + there are four types

Question 4

Organizing Data: Line Listing

What are the four types of variables?

lecture 5

Answer 4

• nominal-scale variable
• ordinal-scale variable
• interval-scale variable
• ratio-scale variable

Question 5

Organizing Data: Types of variables

nominal

define

lecture 5

Answer 5

values are categorized without numerical ranking

(ex: ill or well, dead or alive)

Question 6

Organizing Data: Types of variables

ordinal

define

lecture 5

Answer 6

values are ranked but not necessarily evenly spaced
(ex: stages of breast cancer)

Question 7

Organizing Data: Types of variables

interval

define

lecture 5

Answer 7

measured on a scale of equally spaced units but without a true zero point (ex: shoe sizes, test scores)

Question 8

Organizing Data: Types of variables

ratio

define

lecture 5

Answer 8

an interval variable with a true zero (ex: height, age, sickness duration)

Question 9

Organizing Data: Line Listing

Which variables of the 4 are qualitative variables?

also known as categorical

lecture 5

Answer 9

nominal and ordinal

Question 10

Organizing Data: Frequency Distribution

Which variables of the 4 are quantitative variables?

also known as continuous

lecture 5

Answer 10

interval and ratio

Question 11

Frequency Distributions

What is a frequency distribution?

lecture 5

Answer 11

a table or graph that shows how often different values or group of values appear in a dataset

in public health terms: a way of organizing and presenting health related data to show how often a particular health condition, behavior, or characteristic occurs in a population
- helps identify trends, risk factors, and disparities in health outcomes

Question 12

Frequency Distributions

What are the features/properties of frequency distributions?

lecture 5

Answer 12

• central location
• spread
• shape
• range

Question 13

Frequency Distributions

What is the Gaussian distribution?

also known as normal distribution

lecture 5

Answer 13

the classic symmetrical bell-shaped curve
- no skew

Question 14

spread

lecture 5

Answer 14

how widely dispersed a graph is

Question 15

shape

lecture 5

Answer 15

symmetry

can be symmetrical or asymmetrical (skewed)

Question 16

Shape: Skewness

positive skew

define

Answer 16

central location is to the left of the tail (tail points to the right)

Question 17

Shape: Skewness

negative skew

define

Answer 17

central location is to the right of the tail (tail points to the left)

Question 18

range

lecture 5

Answer 18

measured by spread and distribution

Question 19

Frequency Distributions: Properties

central location

define

lecture 5

Answer 19

where the graph peaks

there are three measures of central location used in epidemiology: mean, median, and mode

Question 20

Central Location: Types of Measures

mean

lecture 5

Answer 20

the average value (add up all the numbers and divide by the amount of numbers that are present)

use:
- has excellent statistical properties; commonly used in statistical manipulations and analyses
- called the center of gravity
- affected by any extreme value

Question 21

Central Location: Types of Measures

median

lecture 5

Answer 21

number in the middle (after being numerically ordered)

use:
- good descriptive measure
- relatively easy to identify
- not often used in statistical manipulations and analyses
- not generally affected by extreme values

Question 22

Central Location: Types of Measures

mode

lecture 5

Answer 22

number that shows up the most

use:
- preferred measure of central location
- can have one or two more
- used almost exclusively as a descriptive measure
- not affected by extreme values

Question 23

Investigating an Outbreak

Why would we investigate an outbreak?

lecture 6

Answer 23

• control or prevention of the health problem
• opportunity to learn / research
• public, political, or legal concerns
• public health program considerations
• training

the most important reason is for control and prevention

Question 24

Investigating an Outbreak

What are the steps of an outbreak investigation?

lecture 6

Answer 24

1. prepare for field work
2. establish the existence of an outbreak
3. verify the diagnosis
4. contruct a working case definition
5. find cases systemically and record information
6. perform descriptive epidemiology
7. develop hypotheses
8. evaluate hypotheses epidemiologically
9. reconsider, refine, re-evaluate
10. compare with lab and/or environment studies
11. implement control and prevention measures
12. initiate or maintain surveillance
13. communicate findings

Question 25

# Investigating an Outbreak: Steps (1) Prepare for field work | define ## Footnote lecture 6

Answer 25

officials discover an increase in the number of cases of a particular disease and then decide that a field investigation is warranted - **scientific and investigate issues:** must have the appropiate scientific knowledge, supplies, and equipment - review applicable literature - assemble useful references (jounrnal articles, sample questionnares) - know what supplies/equipment to protect yourself - have a plan of action - **management and operational issues:** must be a good manager and collaborator because most investigations are conducted by a team rather than just one individual - roles and responsibilities for each members - communications plan to know how often and when to calls with involved agencies, etc. - arrange travel, lodging and local transportation

Question 26

# Investigating an Outbreak: Steps (2) Establish the existence of an outbreak | define ## Footnote lecture 6

Answer 26

verify that the cases are in fact an outbreak; observed cases compared to the number of expected cases - **outbreak or an epidemic:** the occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time

Question 27

# Investigating an Outbreak: Steps (3) Verify the diagnosis | define ## Footnote lecture 6

Answer 27

important because you must ensure that the disease has been properly identified since control measures are often disease specific and to rule out laboratory error as the basis for the increase in reported cases - **review clinical findings and lab results** - **visit one or more patients with the disease to get a better understanding of clinical features** *Helps with generating a hypotheses about disease spread* | just like John Snow did with his investigation

Question 28

# Investigating an Outbreak: Steps (4) Construct a working case defintion | define ## Footnote lecture 6

Answer 28

includes clinical criteria, and may be restricted by time, place, and person - diagnosis may be uncertain early on in an investigation. so, **cases will be classified as suspected, probable, and confirmed**

Question 29

# Investigating an Outbreak: Steps (5) Find cases & record information | define ## Footnote lecture 6

Answer 29

public health workers must look for additional cases to determine the true geographic extent of the problem and the populations affected by it - **passive surveillance:** sending a letter describing the situation and asking for reports of similar cases (*other entities report the data)* - **active surveillance:** telephoning or visiting the facilities *by self* to collect information on any additional cases ***following data is collected:*** - identifying information - demographic information - clinical information - risk factor information - reporter information (source of the report)

Question 30

# Investigating an Outbreak: Steps (6) Perform descriptive epidemiology | define ## Footnote lecture 6

Answer 30

summarizing by time, place, and person - provides a comprehensive characterization of the outbreak - infer the population at risk for disease - provides clues about source, modes of transmission, etc. - begin thinking about where to begin intervention **helps formulate hypotheses**

Question 31

# Investigating an Outbreak: Steps (7) Develop hypotheses | define ## Footnote lecture 6

Answer 31

- if the epidemic curve points to a narrow period of exposure, *what events occurred around that time*? - why do these people living in one particular area have the highest rate of disease - why are some groups at greater risk than others? **answers to these questions assist epidemiogists in formulating their hypothesis**

Question 32

# Investigating an Outbreak: Steps (8) Evaluate hypotheses | define ## Footnote lecture 6

Answer 32

2 ways: 1. compare hypothesis to established facts 2. use analytic epidemiology to quantify relationships: - *retrospective cohort/risk ratio* - *case-cohort/odds ratio*

Question 33

# Analytic Evaluation (Step 8) What does a retrospective cohort study consist of? ## Footnote lecture 6

Answer 33

- small, *well-defined population* - **exposure and outcomes have already occurred** - calculate the attack rate for those exposed to those not exposed - **calculate risk ratio**

Question 34

# Analytic Evaluation (Step 8) How do you calculate the attack rate? ## Footnote lecture 6

Answer 34

attack rate = those **sick** who were exposed/**ALL** exposed attack rate = those **sick** who were not exposed/**ALL** unexposed *high attack rate among those exposed and low attack rate among those **not** exposed = **exposure is a strong suspect***

Question 35

# Analytic Evaluation (Step 8) What is the method for calculating risk ratio? ## Footnote lecture 6

Answer 35

attack rate in **exposed** group/attack rate in **unexposed** group

Question 36

# Analytic Evaluation (Step 8) What does a case-cohort consist of? ## Footnote lecture 6

Answer 36

investigator asks case-patients and **controls** about their exposures and conducts an **odds ratio** to quantify the relationship between *exposure and disease* **controls *need* to be identified in this study**

Question 37

# Analytic Evaluation (Step 8) What is the method for calculating the odds ratio? ## Footnote lecture 6

Answer 37

(number of exposed *cases* **x** number of unexposed *controls*) **/** (number of exposed *controls* **x** number of unexposed *cases*) **or** (AxD)/(BxC)

Question 38

# Statistical significance Why is statistical significance important? ## Footnote lecture 6

Answer 38

implies that the association between the exposure and disease **did not happen by chance**

Question 39

# Investigating an Outbreak: Steps (9) Reconsider, refine, re-evaluate | define ## Footnote lecture 6

Answer 39

done in the case that analytic studies do not provide adequate insight

Question 40

# Investigating an Outbreak: Steps (10) Compare - lab & environmental | define ## Footnote lecture 6

Answer 40

laboratory evidence can **confirm the findings** environmental studies can **explain why an outbreak occurred**

Question 41

# Investigating an Outbreak: Steps (11) Control & prevention | define ## Footnote lecture 6

Answer 41

*primary goal:* to **control** outbreak AND **prevent** additional cases control measure are usally aimed at segments of the **chain of transmission (agent, host, mode of transmission, portal of entry)**

Question 42

# Investigating an Outbreak: Steps (12) Initiate / maintain surveillance | define ## Footnote lecture 6

Answer 42

once control and prevention measures are implemented, they must be **monitored** - this usually comes in the form of **active surveillance** *questions epidemiologists ask:* - are new cases slowing down or stopping - are new cases continuing to occur - where are the new cases, if any - has the outbreak spread outside the original area where interventions were targeted

Question 43

# Investigating an Outbreak: Steps (13) Communicate findings | define ## Footnote lecture 6

Answer 43

**oral briefing for local authorities** - in attendance: local health authorities, those responsible for implementing control and prevention measures (epidemiologists) - investigator describes what they found and recommendations for action **written report** - the usual format (intro, background, methods, etc...) - this may serve as a reference for health departments encountering a similar outbreak in the future