Behavioral Science Flashcards
Case-control study
- Compares a group of people with disease to a group without disease; looks for prior exposure of risk factor
- Odds ratio
Cross-sectional study
- Collects data from a group of people to assess frequency of disease (and related risk factors) at a particular point in time.
- Measures disease prevalence
Cohort study
- Compares a group with a given exposure or risk factor to a group without such exposure; looks to see if exposure increases the likelihood of disease
- Can be prospective or retrospective
- Relative risk
Twin concordance study
- Compares the frequency with which both monozygotic twins or both dizygotic twins develop same disease
- measure heritability and influence of environmental factors
Adoption study
- Compares siblings raised by biological vs. adoptive parents
- measures heritability and influence of environmental factors
Clinical Trial
- Experimental trial involving humans
- Compares 2 therapeutic treatments (2 drugs or drug & placebo)
- Study quality improved when trial= randomized, controlled, and double blind( neither patient or doctor know which treatment group they are assigned)
- Triple blind in when the researchers analyzing the data also dont know
Phase I
Small number of healthy volunteers
-Assesses safety, toxicity and pharmacokinetics
Phase II
Small number of patients with disease of interest
-Assesses treatment efficacy (does it work), optimal dosing, and adverse effects
Phase III
Large number of patients randomly assigned either to treatment or best available treatment (or placebo)
-Compares new drug to current standard of care (is it better or as good?)
Phase IV
Post-marketing surveillance trial of patients after approval
-detects rare of long-term adverse effects; can result in drug being withdrawn from market
Sensitivity
Proportion of all people with disease who test positive or the probability that a test detects disease when disease is present
= TP/(TP+FN)
- SNOUT: a highly SeNsitive test when negative rules OUT disease; as approach 100% false negative rate is lower!
Specificity
Proportion of all people without disease who test negative or the probability that a test indicates non-disease when disease is absent
=TN/(TN+FP)
- SPIN: highly SPecific test rules IN a diagnosis when positive
Positive predictive value (PPV)
Portion of positive test results that are true positives; probability that the person actually has the disease given a positive test result
= TP/(TP+ FP)
** PPV varies directly with prevalence or pretest probability; high pretest probability= high PPV**
Negative predictive value (NPV)
Proportion of negative results that are true negative; probability that person actually is disease free given a negative test result
= TN/(FN+TN)
**NPV varies inversely with prevalence or pretest probability; high pretest probability = low NPV
Incidence
Incidence rate = # of new cases in a specified time period/population at risk during time period
Incidence looks at new incidents!
Prevalence
Prevalence = # of existing cases/ population at risk
Prevalence looks at all current cases
Precision
consistency and reproducibility of a test
-the higher the precision the smaller the standard deviation
Accuracy
The absence of systemic error or bias in the test
- systemic error reduces accuracy
selection bias
Non- random assignment to study group
- Berkson bias: study only looking at inpatients
- loss to follow-up: studying a disease with early mortality
- healthy worker/volunteer bias
-to reduce = randomization
Recall Bias
awareness of disorder alters recall; common in retrospective study
Measurement bias
Information is gathered in a way that distorts it
- Hawthorne effect: groups who know they’re being studied behave differently
- to reduce= use of placebo control groups with blinding
Procedure Bias
subjects in different groups are not treated the same
Observer-expectancy bias
researchers belief in efficacy of a treatment changes the outcome
Confounding bias
When a factor is related to both exposure and outcome, but not on a causal pathway
- to reduce: match patient with similar characteristics in both control and treatment group
Lead time bias
Early detection is confused with increased survival; seen with improved screening techniques
-To reduce= adjust survival according to the severity of disease at time of diagnosis (“back-end survival)
Null Hypothesis
hypothesis of no difference
Alternative hypothesis
Hypothesis of some difference
Type I error
(alpha) ; rejecting the null hypothesis when actually there is no difference; false positive error
- p-value <0.05
Type II error
(beta); failing to reject the null hypothesis when actually there is a difference; false negative error
Power = 1-beta
- to increase statistical power: 1. increase sample size (n), 2. increase precision of measurement, 3. increase expected effect size
Meta-analysis
Pools dats and integrates results from several similar studies to reach overall conclusion
- increases statistical power
- limited by individual study quality or bias in study selection
Confidence interval
Range of values in which a specified probability of the means of repeated samples would be expected to fall CI: mean -Z(SEM) to mean +Z(SEM) - 95% CI corresponds to p=0.05; -Z=1.96 for 95% CI -Z= 2.58 for 99% CI
Confidence interval principles
- if 95%CI for a mean difference between 2 variables includes 0, then there is no significant difference; null hypothesis is not rejected
- if 95% CI for OR or RR includes 1, null hypothesis is not rejected
- if the CIs between two groups do not overlap = significant difference
- if the CIs between two groups overlap= no significant difference exisits
t-test
compares differences between MEANs of TWO groups
ANOVA
Compares MEANS of 3 or more groups
-Ex. comparing the mean blood pressure of 3 different ethnic groups
Chi-Square (X^2)
Compares differences between 2 or more PERCENTAGES or PROPORTION of categorical outcomes
-Ex: comparing the percentage of members of 3 different ethnic groups who have essential hypertension
Pearson correlation coefficient (r)
r is always between -1 and +1
- the closer the absolute value of r is to 1, the stronger the linear correlation between the 2 variables
- positive r value = positive correlation
- negative r value= negative correlation
- coefficient of determination =r^2 (value that is reported)
APGAR
: assessment of newborn @ 1 min and 5 minutes; max of 10 points 2 points per category
Appearance: color
Pulse: >100bpm
Grimace: response to stimulation (mild pinch)
Activity: active motion/muscle tone
Respiration: infant cries well
- >or =7: good, 46 assist and stimulate, <4 resuscitate
