Additional Notes for 1305 CPH Flashcards
What are the 5 Data Collection Methods
Survey Method, Observational study, Experiment, Use of existing studies, Registration method
Questions are asked to obtain information, either through self-administered questionnaire or personal interview
Survey method
- limited to subject’s written answers to
pre-arranged questions - Lower response rate
- Administered to large number of people
- Respondent feel freer to express views
- Respondent feel less pressured to
answer immediately - More appropriate for objective
information
Self-administered questionnaire
- Missing information and vague
responses are minimized - High response rate
- Administered one at a time
- Respondent feel more cautious
- Appropriate for emotionally laden
topics or probing sentiments
Personal Interview
- Attempts to understand cause-and-effect relationships
- Possible to record behavior but only at the time of occurrence
Observational study
- Do not rely on the respondents’
willingness to provide information - Certain types of data can only be collected by observation (example:
behavior pattern) - Potential bias caused by the
interviewing process is reduced or eliminated
Advantages of OS vs Survey
- Things such as awareness, beliefs,
feelings and preferences cannot be
observed - The observed behavior patterns can be
rare or too unpredictable thus
increasing the data collection costs and
time requirements
Disadvantages of OS vs Survey
- Controlled study in which the researcher attempts to understand cause-and-
effect relationships. - “controlled” in the sense that the researcher controls
Experiment
- Census, health statistics, and weather bureau reports
Use of Existing Studies
published or written reports, periodicals, and unpublished documents
Documentary sources
researchers who have done studies on the area of interest are asked personally or directly for information needed
Field measurements
Sampling procedure that gives every element of the population a (known) nonzero chance of being selected in the sample
PROBABILITY
SAMPLING
- Method of selecting n units out of the N units in the population in such a way that every distinct sample of size n has an equal chance of being drawn.
- The process of selecting the sample must give an equal chance of selection to any one of the remaining elements in the population at any one of the n draws.
Simple Random Sampling
Sampling technique where the odds of any member being selected for a sample cannot be calculated
NON-PROBABILITY
SAMPLING
True or False, Clusters may be of equal or unequal size
True
- Population of N units is first divided into subpopulations called strata.
- Then a simple random sample is drawn from each stratum, the selection being
made independently in different strata.
Stratified Random Sampling
- Method of sampling where a sample of distinct groups, or clusters, of elements
is selected and then a census of every element in the selected clusters is taken.
Cluster Sampling
- Method of selecting a sample by taking every kth unit from an ordered
population, the first unit being selected at random
Systematic Sampling
- Divided into a hierarchy of sampling units corresponding to the different
sampling stages - Like cluster sampling, except it involves selecting a sample within each selected
cluster, rather than including all units from selected clusters
Multi-Stage Sampling
- Units are drawn one by one in a sequence without prior fixing of the total number
of observations and the results of the drawing at any stage are used to decide
whether to terminate sampling or not. - The sample size is not set in advance, because you don’t know at the outset how
many times, you’ll be repeating the process.
Sequential Sampling
- Also known as judgment, selective, or subjective sampling
- Sets out to make a sample agree with the profile of the population based
on some pre-selected characteristic. - Useful for situations where you need to reach a targeted sample quickly
and where sampling for proportionality is not the primary concern.
Purposive Sampling
- Selects a specified number (quota) of sampling units possessing certain
characteristics. - In proportional quota sampling you want to represent the major characteristics of
the population by sampling a proportional amount of each.
Quota Sampling
introduction of certain restrictions in order to limit researcher’s
choice of samples
Controlled
resembles convenience sampling; researcher is free to choose
sample group members according to his/her will
Uncontrolled
- One of the most common methods of sampling
- Also known as “Accidental” or “Haphazard” sampling
- Selects sampling units that come to hand or are convenient to get information
from
Convenience Sampling
- Involves the assembling of a sample of persons with known or demonstrable
experience and expertise in some area. - It would be the best way to elicit the views of persons who have specific
expertise. - Provide evidence for the validity of another sampling approach you’ve
chosen
Expert Sampling
- Distribution of health-related
studies - Describes disease occurrence
as to person, place and time - Studies generate hypothesis
Descriptive Epidemiology
- Determinants of health-related
states - Examination of association
between variables - Studies test hypothesis
Analytic Epidemiology
- A detailed account of a patient’s experience and
clinical manifestations that comprise a new or an atypical health event or disease
Case Report
- A study of several subjects manifesting similar signs
and symptoms and linked by a common exposure and experience
Case Series
- The investigator determines through a controlled process the exposure for each individual (clinical trial) or community
(community trial), and then tracks the individuals or
communities over time to detect the effects of the exposure.
Experimental
- The epidemiologist simply observes the exposure and disease status of each study participant
Observational
In this study, a sample of persons from a population are enrolled and
their exposures and health outcomes are measured simultaneously.
* Tends to asses the presence (prevalence) of the health outcome at
that point of time without regard to duration.
Cross -Sectional Study
-Goal: test the efficacy of specific treatments or preventive
measures by assigning individual subjects to one of two or more
treatment or prevention options.
-Analogous to a prospective cohort study, except that the
investigators assign or allocate the exposure (treatment) under
study
Intervention Studies
Two major types of intervention studies
Controlled clinical trials, community interventions
individual subjects are assigned to one or another of the competing interventions
Controlled clinical trials
an intervention is assigned to an entire
group.
Community interventions
is similar in concept to the experimental study.
the investigator selects a group of exposed individuals
and a group of non exposed individuals and follows up both groups to compare the incidence of disease(or rate of death from disease)in the two groups.
Cohort Study
An alternative
type of cohort study.
* In this type of study both the exposure and the outcomes have already
occurred
Retrospective Cohort Study
the investigator
identifies the original population at the
beginning of the study.
Follow-up or Prospective Cohort Studies
- To examine the possible relation of an exposure to a certain disease, we identify a group of individuals with that disease (at CDC such persons are called case-patients rather than cases, because case refers to occurrence of
disease, not a
person).
Case-Control Study
