Type I error - ANSWER Rejecting null hypothesis when it is true
Type II error - ANSWER failing to reject a false null hypothesis
cohort study - ANSWER Follows a group of people to track risk factors and outcomes
overtime
Groups are defined regarding their EXPOSURE to a factor of interest.
(perspective or longitudinal studies)
Followed-up to determine differences in rates at which disease develops in relation to expo-
sure.
Start with a sample of individuals with and without EXPOSURE to a potential risk factors who
are followed for incidence of the outcome in each group. They can also be done retrospec-
tively. Cohort studies have less patient selection and stronger evidence of causal association.
Yields incidence rates, relative risk, attributable risk
More EXPENSIVE
Case-control study - ANSWER Compares histories of a group of people with a condition to
a group of people without the condition.
1
,Begins with the identification of individuals who have the OUTCOME of interest.
After case-control status is defined, exposures are assessed and evaluated.
Good for studying rare outcomes or outcomes that develop over a long time.
Determine if two groups differ in exposure.
(Case reference, case comparison. Or retrospective studies)
Examine the population of individuals with and without an outcome of interest, study for ex-
posure to one or more risk factors. The studies are quicker, less expensive, and easier.
Generally yields only estimate of relative risk (odds ratio).
Example: Foodborne illness investigations
cross-sectional study - ANSWER Assesses the prevalence of an outcome in a broad popu-
lation at one point in time.
Provide a "snapshot" of a population at a moment in time.
Point Prevalence.
(Prevalence, correlation or survey studies)
Exam in the outcome and risk factors reviewed in a population group at one point in time. In
the studies the outcomes are measured the incidence rate cannot be determined.
2
,case reports/series - ANSWER Detailed history of a small number of individual cases
quasi-experiment - ANSWER Non-randomly assigned groups of patients to receive either
a treatment or placebo
Randomized-controlled trial - ANSWER Randomly selects a group of patients to receive a
treatment and Another to receive placebo
systematic review and meta-analysis - ANSWER Collects all previous studies on the topic
and statistically combined their results
Sensitivity - ANSWER The ability of a test to detect ALL TRUE cases of the disease.
= (Number of true-positive results) / (the number of true-positive + false-negative results)
High sensitivity = High False Positives.
High sensitivity = TRUE NEGATIVES. You will not have any false negative tests.
Specificity - ANSWER The ability of a test to correctly identify a negative result.
= (Number of true-Negative results) + (Number of False-Positive results)
High Specificity = TRUE POSITIVES. you will not have any false positive tests.
High chance for false negatives.
3
, Positive Predictive Value (PPV) - ANSWER TP/(TP+FP)
Negative Predictive Value (NPV) - ANSWER TN / (TN + FN)
Bacterial meningitis CSF analysis - ANSWER Cloudy
Increased neutrophils
Increased Protein
Decreased Glucose
Increased WBC
Viral meningitis CSF analysis - ANSWER Clear/hazy
Normal to increased protein
Normal to decreased glucose
Normal to increased WBC
Normal to increase lymphocytes
Normal to increased monocytes
Normal to decreased neutrophils
Fungal meningitis CSF analysis - ANSWER Clear/hazy
Increase WBC's
Normal to increase protein
Normal to decreased glucose
Normal to increase lymphocytes
Normal to increased monocytes
Normal to decreased in neutrophils
Increased Agglutination capacity
4
Type II error - ANSWER failing to reject a false null hypothesis
cohort study - ANSWER Follows a group of people to track risk factors and outcomes
overtime
Groups are defined regarding their EXPOSURE to a factor of interest.
(perspective or longitudinal studies)
Followed-up to determine differences in rates at which disease develops in relation to expo-
sure.
Start with a sample of individuals with and without EXPOSURE to a potential risk factors who
are followed for incidence of the outcome in each group. They can also be done retrospec-
tively. Cohort studies have less patient selection and stronger evidence of causal association.
Yields incidence rates, relative risk, attributable risk
More EXPENSIVE
Case-control study - ANSWER Compares histories of a group of people with a condition to
a group of people without the condition.
1
,Begins with the identification of individuals who have the OUTCOME of interest.
After case-control status is defined, exposures are assessed and evaluated.
Good for studying rare outcomes or outcomes that develop over a long time.
Determine if two groups differ in exposure.
(Case reference, case comparison. Or retrospective studies)
Examine the population of individuals with and without an outcome of interest, study for ex-
posure to one or more risk factors. The studies are quicker, less expensive, and easier.
Generally yields only estimate of relative risk (odds ratio).
Example: Foodborne illness investigations
cross-sectional study - ANSWER Assesses the prevalence of an outcome in a broad popu-
lation at one point in time.
Provide a "snapshot" of a population at a moment in time.
Point Prevalence.
(Prevalence, correlation or survey studies)
Exam in the outcome and risk factors reviewed in a population group at one point in time. In
the studies the outcomes are measured the incidence rate cannot be determined.
2
,case reports/series - ANSWER Detailed history of a small number of individual cases
quasi-experiment - ANSWER Non-randomly assigned groups of patients to receive either
a treatment or placebo
Randomized-controlled trial - ANSWER Randomly selects a group of patients to receive a
treatment and Another to receive placebo
systematic review and meta-analysis - ANSWER Collects all previous studies on the topic
and statistically combined their results
Sensitivity - ANSWER The ability of a test to detect ALL TRUE cases of the disease.
= (Number of true-positive results) / (the number of true-positive + false-negative results)
High sensitivity = High False Positives.
High sensitivity = TRUE NEGATIVES. You will not have any false negative tests.
Specificity - ANSWER The ability of a test to correctly identify a negative result.
= (Number of true-Negative results) + (Number of False-Positive results)
High Specificity = TRUE POSITIVES. you will not have any false positive tests.
High chance for false negatives.
3
, Positive Predictive Value (PPV) - ANSWER TP/(TP+FP)
Negative Predictive Value (NPV) - ANSWER TN / (TN + FN)
Bacterial meningitis CSF analysis - ANSWER Cloudy
Increased neutrophils
Increased Protein
Decreased Glucose
Increased WBC
Viral meningitis CSF analysis - ANSWER Clear/hazy
Normal to increased protein
Normal to decreased glucose
Normal to increased WBC
Normal to increase lymphocytes
Normal to increased monocytes
Normal to decreased neutrophils
Fungal meningitis CSF analysis - ANSWER Clear/hazy
Increase WBC's
Normal to increase protein
Normal to decreased glucose
Normal to increase lymphocytes
Normal to increased monocytes
Normal to decreased in neutrophils
Increased Agglutination capacity
4
