Evaluative Sciences Flashcards
Allow for the evaluation of multiple exposures that may increase risk for a specific disease.
Case-control studies
Subjects are selected based their exposure status.
Cohort Studies
Subjects are selected based on their disease status.
Case-Control Studies
comparing the presence of periodontitis in diabetics vs. non-diabetics
Chi-squared test
Formula for incidence rate
(# of new cases of disease/population at risk ) over a time period
Is a range of values about a sample statistic that we are confident that the true population parameter lies.
Confidence intervals
cannot directly compute incidence of disease in exposed and non-exposed persons
case-control
P-value Is the ______ assuming that the _____ is true, of seeing an _______ than that in the study by chance.
P-value Is the probability, assuming that the null hypothesis is true, of seeing an effect as extreme or more extreme than that in the study by chance.
Follows a mathematical order but has no true zero
Interval scale
compares disease prevalence in the exposed and unexposed.
Prospective cohort: c
threat to internal validity
bias, error, and confounding
is a statistical method that allows for comparison of several population means.
ANOVA
Efficient for rare diseases.
Case-control studies
they begin with the exposure of interest and probe back for exposure information.
Retrospective cohort:
Provides complete description of experience after exposure, including rate of progression and natural history of disease
Cohort Studies
significance of r2
The higher the r2 the better the fit of the regression line.
In case-control studies, cases and controls must have had an
equal chance of being exposed
the usual occurrence of a disease in a given population
endemic
selection of subjects based on neither exposure or disease status
cross-sectional studies
studies are selected based on their exposure status
cohort studies
Can study multiple diseases/outcomes from a given exposure
Cohort Studies
Follows a mathematical order and has a defined true zero
Ratio Scale
are sub-types of cohort studies in which exposure (i.e treatment) is randomly assigned by the investigator
Randomized Clinical Trial (RCT )
Instructs the search engine to retrieve the information with a broad subject heading that are broken down into narrower subject headings
Explode
Cannot directly compute incidence of disease in exposed and non-exposed persons.
Case-control studies
What are considered the best types of evidence? (2)
Systematic Reviews and RCT
drawing different conclusions depending on their knowledge of which study arm particular partcipant is in
information bias
When examining categorical data, this test can be used to compare the proportion of subjects in each of two groups who have a dichotomous outcome.
Chi-squared test
the participant does not know but investigator does know treatment assignment.
Single blinded:
Does the exposure precede the disease?
E—>D
exposure of interest
independent variable
can demonstrate risk indicators and not risk factors due to the retrospective nature of the study
case-control
this is often the one the researcher thinks is the “truth”.
H a :
Name 3 observational studies
Cohort studies. Case control studies. Cross-sectional studie
only certain values possible in a range
Discrete
systematic complete summary of the literature
systematic review
Formula for prevalence?
(# of cases/#person in population) at a specified time
Good for assessing rare exposures and rapidly fatal diseases.
Cohort studies
data falls into a category, but no order to data
Nominal:
outcome of interest
dependent variable
failing to reject (accept) the null hypothesis that is actually false in the population
β (beta)
What are considered the lowest levels of evidence?
expert opinions and case reports
Considerations in experimental studies
Stopping rules Sample size Analysis and Interpretation
drawing different conclusions depending on their knowledge of which study arm particular participant is in
selection bias
not optimal for rare exposures
case control
Usually states that there is no difference between two groups being compared or no effect of a product or intervention.
H :
uses names
Nominal
What is the formula for impact factor?
IF= # citations in year/ total # articles published past 2 y
“point-in-time” or “snapshots” information.
Cross-sectional studies
These studies follow participants in time.
Cohort Studies
Maintains temporal sequence, ie, assesses exposure before outcome
Cohort Studies
(generalizability)
External validity
Name four types of scales used for quantification in epdiemiology
Nominal scale
Ordinal
Interval
Ratio
A variable is a confounder if:
- It is a known risk factor of the outcome. 2. It is associated with the exposure but is not the result of the exposure.
can be used when the outcome variable of interest is only being examined in one group (testing difference from 0 or some given value).
one-sample t-test
Usually states that there is a difference between two groups being compared or an effect of a product or intervention.
H a :
a meaningful increase in the occurrence of a disease in a given population
epidemic
community intervention trials
experimental studies
Cases and controls should be different only on their
past exposure
best form of studies?
systematic reviews and meta-analyses
of cases/#person in population at a specified time
Prevalence Proportion
Most basic study design.
Cross-sectional studies
spread of a disease across a large region or worldwide
pandemic
the degree to which the results of a study are likely to approximate to the ‘truth’
Internal validity
Can calculate incidence among exposed and unexposed.
Cohort studies
the extent to which the effects observed are applicable to a broader population
External validity
Exposure and disease are assessed at the individual level
Cross-sectional studies
Not optimal for rare exposures.
Case-control studies
this study does not need explained etiologic objectives
cross-sectional studies
point in time or snapshots information
cross-sectional studies
α is commonly (but not always) set to 0.05, and is interpreted AS ?
as the maximum chance (5%) of incorrectly rejecting the null hypothesis when it is actually true.
Conducting a search steps
- Defining the question. 2. Choosing a resource. 3. Keyword searching vs. classification systems. 4. Search techniques.
Follows an order based on severity
Ordinal scale
Temporality cannot be assessed
Cross-sectional studies
T/F Incidence is a rate and is not meaningful without a time unit.
T
can calculate incidence among exposed and unexposed
Cohort Studies
where neither participant nor investigator know tx assignment
randomized control trials
Are used to appropriately group the terms and operators to control the order of the search.
Parentheses
if P-value is > α.
Fail to reject the null hypothesis
of new cases of disease/population at risk over a time period
Incidence Rate
Good for assessing rare exposures and rapidly fatal diseases
Cohort Studies
can be used when subjects are matched in pairs and their outcomes are compared within each matched pair (including where observations are taken on the same subjects before and after a given intervention).
matched-pair t-test
Sampling and analytic methods provide for statistically valid inference to populations
Cross-sectional studies
Statistical test that can be used to determine whether the mean value of a continuous outcome variable differs significantly between two independent groups.
t-test
systematic complete summary of the literature Cochrane Collaboration: http:
Systematic Review
Define Pico
P= Patient or Problem I= Intervention C= Comparison (if relevant) O= Outcomes
Minimizes error in ascertainment of exposure (at least if prospective)
Cohort Studies
Group of interest (smokers) with comparison group non-smokers and follow over time to compare outcomes
Cohort Studies
rejecting the null hypothesis that is actually true in the population.
Type I Error:
can study diseases with long latency periods
case-control studies
Comparing the mean years of survival for implants in women vs. men to see if they differ significantly.
t-test
Name 3 types of observational studies
Cohort Studies
Case Control Studies
Cross-sectional studies
Prevalence is a rate. T/F
False. Prevalence is not a rate; the term “prevalence rate” should not exist
test hypothesis.
H 0 :
an event, condition, or characteristic that preceded the disease and without which the disease would not have occurred at all or would not have occurred until some later time
cause
• Inefficient for rare diseases.
Cohort studies
inference can only correctly be made to the population from which the sample was drawn
External validity
combined analysis of data from different studies following strict guidelines
meta-analysis
With regards to diagnosis, prognosis, or causation what type of studies are the most accurate?
longitudinal studies like cohort studies
Ex: how often do you brush your teeth? (never, few times/month, few times/week, every day)
Ordinal:
what are boolean operators
and/or/not
must have had an equal chance of being exposed in case-control studies
Cases and controls
they observe the outcomes without intervening to affect them
observational studies
we often leap to inference far beyond the targeted population
External validity
Case-control studies should theoretically mimic
cohort studies
What type of study is this
Group of interest (eg cancer patients)
with comparison group (non-patients), take histories, compare histories and draw conclusions
case-control
Situation is which a non-causal association between a given exposure and an outcome is observed as a result of the influence of a third variable
Confounding
relatively efficient in terms of time and money
case-control studies
Many search engines allow you to place a symbol at the end of a word, which tells the engine to retrieve the word stem with different endings. A common symbol used is asterisk (*) although this is not universal.
Truncation
•Power is calculated as _____and is related to the _____ used in the study
•Power is calculated as (1-β) and is related to the sample size used in the study
where neither participant nor investigator know treatment assignment.
Double blinded:
combined analysis of data from different studies following strict guidelines
Meta-analysis
The level of statistical significance is described as
(alpha).
study recruiters can be eager to recruit “sick person” into experimental arm
selection bias
Systematic error in the design, conduct or analysis of a study that results in a mistaken estimate of an exposure’s effect on disease.
Bias
In this study, the temporal relationship cannot be established with certainty.
Case-control studies
data has a specific order to it
Ordinal:
most basic study design
cross-sectional studies
Diseased people are compared to non- diseased people.
Case-control studies
The researcher manipulates the exposure (usually a drug or treatment) to compare it to the standard of care.
Experimental studies
The primary purpose of randomization of RCTs is the minimizing of
confounding
if P-value is ≤ α
Reject the null hypothesis
includes most books, review articles, and indexes to the literature, and usually summarize, reivews or organize information
Secondary Source
must be the first disclosure containing sufficient information to enable peers to assess observations, repeat experiements and to evaluate intellectual processes
Primary Sources
how the study was carried out is a measure of
internal validity
do the findings apply to my patient is a measure of
external validity
