Biostats Flashcards
mode
most frequent values
median
center value arranged from lowest to highest
Range
highest - lowest
Gaussian or normal distribution curvw
the mean, median, and mode are the same values
Skew
refers to the direction of the tail.
left skew (negative): more higher values
Right Skew (Positive): More lower values
Null Hypothesis
No statistically significant difference in the groups. what the person tries to reject
Alternative hypothesis
There IS a statistically significant difference
what the person tries to prove
Confidence Interval
CI = 1 - alpha
if it does not cross 0 or 1 it is significant
Type 1 error
False positive = Alpha
Type 2 error
False Negative = Beta
Power
Power = 1 - Beta
Is determined by outcome values, rate and significance
Risk
of unfavorable events in group / Total # in group
Relative Risk (RR)
Risk in Txt group / Risk in Control Group
RR = 1 no difference in risk
RR > 1 greater risk of the outcomes
RR < 1 lower (reduced) risk
Relative Risk Reduction (RRR)
1 - RR
Measures how much less likely the events risk is in the treatment group relative to the control group
Absolute Risk Reduction (ARR)
(% risk in control) - (% risk in treatment group)
Number needed to Treat (NNT)
1 / (ARR = % risk in control - % risk in txt)
Always round up no mater what
Odds Ratio (OR)
Estimates the risk associated with the treatment or intervention in a case control study
Hazard Ration (HR)
Hazard rate in txt group / HR in cont group
Discrete Data (Categories)
Nominal (Categorical) Data - ordeer doesnt matter
EX: Sex, ethnicity, marital statis, religous preference
Discrete Data (Rank in ORDER)
Ordinal Data - order matters
Ranked categories Ex: NYHA FC Class ranking, Pain scale 8 is worse than 7
Continous Data (most measurements)
Ratio Data - meaningful values with a true meaningful 0. 0 = none
EX: Blood pressure ( 0 = death), time, wt, ht
Continuous Data
Interval Data - meaningful values but without a meaningful 0
Ex: Temp
Student t-test
Assess significance in studies with continuous data
Chi-Square Test
Assess significance between treatment groups in a discrete data (nominal or ordinance)
Independent variable
is manipulated by the researcher
Ex: drug doses, placebos
Dependent variables
Comorbidity like HF diabetes, BP,
Types of medical Studies
In order of most reliable to least
Systematic review and Meta > RCT> Cohort> case-contolled > case series/report> expert opinion
Case-control study
Compares patients with a disease (cases) to those without the disease (control). the researcher looks back retrospectively
Cohort Study
Compares outcomes of a patients exposed (txt) and not exposed (control) to a txt. The researcher looks progressively
Cross-sectional survey
Estimates the relation between variables and outcomes at one particular time in a defined population
Case report/Series
Describing a unique adverse reaction or unique condition that appears in a single patient (report) or few patients (series)
Think attridge starting one for the C.Diff bacteremia
Randomized controll trial (RCT)
Compares and expiremental treatment to a control (placebo or standard) to determine which is better.
Contains Inclusion and exclusion criteria
RCT crossover
Group 1 recieves txt a then switches to txt b
Group 2 recieves txt b then switches to a
RCT factorial
randomizes more than the two usual groups
Meta-analysis
Combines results from multiple studies in order ot develop a conclusion that has a greater statistical power than from the smaller studies
Systematic Reviews
Summary of the clinical literature that focues on a specific topic or question.
Think about the systematic review you included in the letter to the editorial.
