Behavioral Sciences Flashcards
What is a cross-sectional study?
collects data from a group of people to assess frequency of disease at a particular point in time
What is the primary limitation of a cross-sectional study?
while it can demonstrate risk factors associated with a disease, it does not establish causality
What is a case-control study?
one that compares a group of people with disease to a group without disease and looks for prior exposure or risk factors
What is a cohort study?
one that compares a group with a given exposure or risk to a group without such an exposure to see if exposure affects the likelihood of disease
A case-control study can be used to calculate the ___ while a cohort study can be used to calculate the ___.
- case-control: odds ratio
- cohort study: relative risk
What elements of a clinical trial can be used to improve the quality of such a study?
- randomization
- controls
- double- or triple-blinding
What is a triple-blind study?
one in which the treatment recipients, treatment providers, and data analyzer are all “blind”
What are the four phases of a clinical trial? Describe the group of subjects used for each and what is being assessed?
- phase I: small number of healthy volunteers used to assess safety, toxicity, pharmacokinetics and pharmacodynamics
- phase II: small number of patients with disease used to assess whether it works (efficacy, optimal dosing, adverse effects)
- phase III: randomized study in which patients are assigned to either the treatment under investigation or to the best available treatment/placebo used to determine if it is good or better than the current standard of care
- phase IV: surveillance of patients after the treatment has been approved used to detect rare or long-term adverse effects
How are PPV and NPV calculated?
PPV = TP/(TP + FP) = proportion of positive test results that are true positives NPV = TN/(TN + FN) = proportion of negative test results that are true negatives
Describe PPV in words.
the probability that a person who has a positive test result actually has the disease
Describe NPV in words.
the probability that a person with a negative test result actually does not have the disease
What is pretest probability?
the baseline risk of the population from which the individual is pulled (i.e. prevalence within the population)
How does pretest probability relate to PPV and NPV?
- PPV varies directly with pretest probability
- NPV varies inversely with pretest probability
PPV and NPV vary according to what other measure?
pretest probability
Why do we typically use sensitivity and specificity rather than PPV and NPV?
because sensitivity and specificity are fixed properties of a test whereas PPV and NPV vary based on pretest probability
Describe sensitivity in words.
the probability that when the disease is present, the test is positive
Describe specificity in words.
The probability that when the disease is absent, the test is negative
How are sensitivity and specificity calculated?
sensitivity = TP/(TP + FN) = proportion of people with the disease who test positive specificity = TN/(TN + FP) = proportion of people without the disease who test negative
How do sensitivity and specificity mathematically relate to the false-negative and false-positive rate, respectively?
sensitivity = 1 - false negative rate specificity = 1 - false positive rate
What is the difference between incidence and prevalence?
- incidence looks at new cases in the given time frame
- prevalence looks at all cases that exist at a specific point in time
For what sorts of diseases does prevalence nearly equal incidence?
those with a short duration of disease
How is the odds ratio calculated?
ad/bc (cross multiple)
Odds ratios are typically reserved for what kind of study?
case-control studies
How is relative risk calculated?
RR = [a/(a+b)]/[c/(c+d)] = risk of developing disease in the exposed group divided by risk in the unexposed group
Relative risk is typically reserved for what kind of studies?
cohort studies
Give an example of relative risk calculation.
21% of smokers get lung cancer and 1% of non-smokers do, so RR = 21/1 = 21
How is attributable risk calculated?
a/(a+b) - c/(c+d)
Give an example of attributable risk.
21% of smokers get lung cancer and 1% of non-smokers do, so smoking has an AR of 20%
How is relative risk reduction calculated?
1 - RR
Give an example of relative risk reduction.
if 2% of vaccinated individuals get the flu and 8% of unvaccinated individuals do, then RR= 2/8 and RRR = .75
How is absolute risk reduction calculated?
c/(c+d) - a/(a+b)
Give an example of absolute risk reduction.
if 2% of vaccinated individuals get the flu and 8% of unvaccinated individuals do, then ARR is 6%
How is NNT calculated?
1/ARR
How is NNH calculated?
1/AR
What is the difference between a test’s precision and accuracy?
- precision (aka reliability): consistency and reproducibility
- accuracy (aka validity): absence of systematic error or bias
Which kinds of error decrease the precision of a test? Which kind decreases the accuracy of a test?
Random error decreases the precision
Systematic error decreases the accuracy
What two effects does increasing precision of a test have on analysis of the results?
- reduces standard deviation
- increases statistical power (1-B)
The most common type of selection bias is what?
sampling bias
How can selection bias be reduced?
randomization
What is the Berkson bias?
a type of selection bias based on the idea that a study population selected from a hospital is less healthy than the general population
What is the healthy worker effect?
a type of selection bias based on the idea that a study population selected from those in the work force is healthier than the general population
Define procedure bias.
subjects in different groups are not treated the same
How can procedure bias be avoided?
placebos and blinding help reduce the influence of participants and researchers on procedures and interpretation
Patients in the treatment group spend more time in highly specialized hospital units. This is an example of what kind of bias?
procedure bias
Define the observer-expectancy bias.
a researcher’s belief in the efficacy of a treatment changes the outcome of that treatment
How can observer-expectancy bias be avoided?
placebos and blinding help reduce the influence of participants and researchers on procedures and interpretation
Define a confounding variable.
one that is related to both the exposure and outcome but not on the casual pathway between the two, which tends to confuse the effect of the exposure on the outcome
How can confounding bias be avoided?
matching or randomization
What is lead-time bias?
the idea that early detection can be confused with an increase in survival even though the natural history of the disease has not changed
How can lead-time bias be avoided or reduced?
measure “back-end” survival (adjust survival according to the severity of the disease at the time of diagnosis)
What measure of central tendency is most affected by outliers? Which is least affected?
- mean is most affected
- mode is least affected
Define standard deviation and standard error of the mean using words.
- SD is how much variability exists from the mean in a set of values
- SEM is how much variability exists between the sample mean and the true population mean
How is standard deviation calculated?
such that 1 standard deviation includes the central 68% of data points, 2 SDs includes 95%, and 3 includes 99.7%
1 SD includes ___ of the data, 2 includes ___, and 3 includes ___.
- 1 SD = 68%
- 2 SD = 95%
- 3 SD = 99.7%
How is variance calculated?
variance = SD^2
How is SEM calculated?
SEM = SD/srt(n)
How does SEM chance as n increases?
SEM decreases
A bimodal distribution of data suggests what?
there are two different populations
Describe the shaped of a positively skewed distribution.
an asymmetric distribution with the tail on the right
Describe the shaped of a negatively skewed distribution.
an asymmetric distribution with the tail on the left
For a normal distribution, the mean = median = mode. How does the mean compare to the median and mode in a positively skewed distribution? A negatively skewed one?
- positive: mean > median > mode
- negative: mean < median < mode
Define type I and type II errors.
- type I: stating there is a difference when none exists
- type II: stating there is no difference when one exists
With regards to error and statistical analysis, what are alpha and beta?
- alpha is the probability of making a type I error (you “Abserved” a difference that did not exist)
- beta is the probability of making a type II error (you were Blinded to the truth)
How do we determine the probability of making a type I error?
- the probability equals alpha
- alpha is usually predetermined and is used as the cutoff value for p (i.e. if p<0.05 then we reject the null hypothesis, alpha was set at 5%)
How do we determine the probability of making a type II error?
- the probability equals beta
- beta is related to the statistical power (1-B)
What three things can you do to increase the power of a study and reduce the probability of making a type II error (B)?
- increase sample size
- increase the expected effect size
- increase the precision of the measurement
Under what three conditions are confidence intervals able to help us reject the alternate hypothesis?
- if the CI for a mean difference between two groups includes 0
- if the CI for an odds ratio or relative risk ratio includes 1
- if the CIs between two groups overlaps
How is confidence interval calculated?
CI = mean +/- Z(SEM) where Z = 1.96 for a 95% CI and 2.58 for a 99% CI
What is t-test used for?
comparing the means of two groups
What is an ANOVA test used for?
comparing the means of three or more groups
What is a chi-square test used for?
checking the differences between two or more percentages or proportions of categorical outcomes (i.e. not the mean blood pressure between three ethnic groups but the percentage of three different ethnic groups who have essential hypertension)
How does an ANOVA test differ from a chi-square test?
- the ANOVA is used to compare the means of three groups
- the chi-square is used to compare the percentages of people in those groups with a given outcome
What is the principle of nonmaleficence?
the obligation of a doctor to “do no harm” (must be balanced with beneficence in such cases that benefits outweigh the harms like in surgery)
What is the principle of justice?
the obligation of a physician to treat people fairly and equitably (but not always equally as is the case with triage)
What are the four aspects of informed consent?
- disclosure
- understanding
- capacity
- voluntariness
What is therapeutic privilege?
an exception to informed consent whereby information can be withheld if disclosure would severely harm the patient or undermine informed decision-making
What must be true about a patient and his or her decision for him or her to be considered to have “decision making capacity”?
- over 18 or legally emancipated
- makes and communicates a choice
- patient is informed
- decision remains stable
- decision is consistent with patient’s values and goals
- decision is not a result of altered mental status
What three things can make an oral advanced directive more valid?
- it was specific
- it was repeated
- it was repeated to multiple people
Under what circumstances is a surrogate-decision maker used?
if a patient loses decision-making capacity and has not prepped an advanced directive
In what order are family members allowed to be surrogate decision makers?
spouse then adult children and then parents
What sexual changes are observed in the elderly?
- libido stable in men but declines in post-menopausal women
- men slower to erection and ejaculation with longer refractory period
- women have vaginal shortening, thinning, and drying
What changes in intelligence do the elderly typically experience?
intelligence does not decrease
What body composition changes are expected in the elderly?
reduced muscle mass and increased fat mass
What changes in sleep are seen in the elderly?
- less REM and slow-wave sleep
- increased sleep onset latency and increased early awakenings
What is presbycusis?
sensorineural hearing loss of higher frequencies due to destruction of hair cells at the cochlear base
What are primary, secondary, tertiary, and quaternary disease prevention?
- primary: prevent disease (e.g. vaccination)
- secondary: screen early and manage asymptomatic disease
- tertiary: treat to reduce complications
- quaternary: identify patients at risk of unnecessary treatment and protect them from the harm of new interventions
What does quaternary disease prevention consist of?
identifying patients at risk of unnecessary treatment and protecting them from the harm of new interventions
Who is medicare available to?
- those over the age of 65
- those under 65 with certain disabilities
- those with end-stage renal disease
What are the four parts of Medicare?
- Part A: hospital insurance
- Part B: basic medical bills
- Part C: delivered by approved private companies
- Part D: drugs
What is “safety culture”? Why is it important?
- an environment in which people can freely bring up safety concerns without fear of censure
- this facilitates error identification
What is the PDSA cycle used for? What are the steps?
- it is a process improvement model used to test changes in a real clinical setting
- Plan, Do, Study, Act
What is meant by “forcing functions”?
it is a design concept whereby the design of a process or tool prevents undesirable actions (e.g. it is impossible to connect the feeding syringe to IV tubing)
What is the most effective way to reduce clinical errors?
“forcing functions” - designing tools and processes so undesirable actions are impossible (e.g. it is impossible to connect the feeding syringe to IV tubing)
What are the three primary quality measurements used to judge a new system or process? Define each.
- outcome: impact on patients
- process: performance of system as planned
- balancing: impact on other systems/outcomes
What is the “Swiss cheese model” in public health?
the idea that in complex organizations, flaws in multiple processes and systems may align to cause patient harm
What are active and latent medical errors?
- active: occurs at the level of the operator and have an immediate impact
- latent: occurs indirect from the operator but still impact patient care (i.e. these are accidents waiting to happen)
Different types of IV pumps are used within the same hospital. What type of medical error is this?
latent rather than active
Define the two types of medical error analysis: root cause analysis and failure mode and effects analysis
- root cause: a retrospective approach that uses records and participant interviews to identify what led to an error
- mode and effects: a forward-looking approach that uses reasoning to identify the ways a process might fail and prioritize them according to probability and severity of impact
