Quick Stats: Basics for Medical Literature Evaluation
by Charles Herring, PharmD, BCPS, CPP
Trade paperback: 78 pages
ISBN: 1-59399-210-6
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Book ID: 10709-1-1
Quick Stats: Basics for Medical Literature Evaluation About this book

This book is a primer for basic medical literature evaluation. It is not intended to be used as a complete critical literature evaluation text. It is simply a “survival guide” for students and clinicians trying to learn the basics of literature evaluation.

About the author

Dr Herring graduated from the University of North Carolina in 1992 with a Bachelor of Science in Pharmacy and in 1994 with a Doctor of Pharmacy. His post-doctoral residency in pharmacy practice was completed at the Medical University of South Carolina in Charleston, South Carolina in 1995.

 

Dr. Herring is currently an Assistant Professor of Pharmacy Practice at the Campbell University School of Pharmacy in Buies Creek, North Carolina. He is also the Adult Medicine Team Clinical Pharmacist Practitioner (CPP) for the Downtown Health Plaza of Wake Forest University Baptist Medical Center in Winston-Salem, North Carolina.

 

Charles Herring, PharmD, BCPS, CPP


Table of Contents

Basic Concepts

Sample vs Population

  • Randomization

 

Variables

  • Random
  • Independent
  • Dependent

 

Analysis

  • Univariable
  • Bivariable
  • Multivariable

 

Types of Data

  • Non-parametric
    • Nominal
    • Ordinal
  • Parametric
    • Interval
    • Ratio

 

Distributions

  • Normal
  • Bimodal
  • Rectangular
  • Skewed
    • Positive Skew
    • Negative Skew
    • Kurtosis

Descriptive Statistics

Measures of Central Tendency

  • Mean
  • Median
  • Mode
  • Gaussian or Normally distributed data graph
  • Positively skewed data graph
  • Negatively skewed data graph

 

Measures of Variability

  • Range
  • Interquartile Range
  • Variance
  • Standard Deviation
  • Coefficient of Variation
  • Standard Error of the Mean (aka standard error)
  • Confidence Intervals
    • Interpretation of Superiority Traits
      • Interpretation for Differences
      • Interpretation for Ratios
    • Interpretation of Equivalence Trials
    • Interpretation of Non-Inferiority Trial

Sensitivity, Specificity, Predictive Value, and Hypothesis Testing

Sensitivity

Specificity

Positive Predictive Value

Negative Predictive Value

Prevalence

Incidence

Hypothesis Testing

  • Null Hypothesis
  • Alternative Hypothesis
  • Type 1 or Alpha Error
    • p-value
  • Type 2 or Beta Error
    • Power

 

Sample size calculations

Correcting for estimated Drop-out Rate

Delta

One-tailed vs Two-tailed tests

Effect of change in Alpha

Effect of change in Beta

Effect of change in Delta

Effect of One-tailed vs Two-tailed design

Effect of change in expected incidence

Statistical Inference Techniques for Hypothesis Testing w/ Parametric Data

T-test

  • Non-Paired
  • Paired
  • One-Tailed
  • Two-Tailed
  • Bonferroni
  • Dunn-Sidak

 

ANOVA

  • ANOVAs for Non-Paired samples
    • 1-way ANOVA
    • Multifactorial ANOVAs
      • 2-way
      • 3-way
      • 4-way
      • etc
  • ANOVAs for Paired samples
    • Repeated Measures ANOVA
    • 2-way Repeated Measures ANOVA
    • Repeated Measures Regression
  • Multiple Comparison Methods (Post Hoc Analysis)
    • Least Significant Difference
    • Layer (aka stepwise) Methods
      • Newman-Keuls
      • Duncan
    • Experiment-wise Methods
      • Dunnett
      • Dunn
      • Tukey
      • Scheffe

Statistical Inference Techniques for Hypothesis Testing w/ Non-Parametric Data

Non-Parametric Tests for Nominal Data

  • Chi-Square Tests
    • Test of Independence
    • Goodness of Fit
    • McNemar Chi-Square
    • Mantel-Haenszel Chi-Square
    • Log-Linear Analysis
    • Post Hoc Analysis
  • Fisher's Exact
  • Rows by Columns Test
  • Table Noting Proper Test to Use

 

Non-Parametric Tests for Ordinal Data

  • Mann Whitney U and Wilcoxon Rank Sum
  • Kolmogorov-Smirnov
  • Wilcoxon Signed Rank
  • Kruskal-Wallis
  • Friedman
  • Table Noting Proper Test to Use

Correlation and Regression

Correlation

  • r-value
  • population correlation coefficient
    • coefficient of determination (r2)
  • sample correlation coefficient

 

Regression

  • Multiple regression
  • Linear regression
  • Logistic regression
  • Cox Proportion Hazards

Error vs Bias

Bias in the Publication Process

  • Funding Sources
  • Publication
    • Negative Study
  • Investigator
  • Reviewer
  • Small study

 

Compliance

Prevalence

Selection Bias

  • Inclusion in study
  • Participation in study
  • Admission rate
  • Nonresponse
  • Membership
  • Diagnostic or Detection
  • Insensitive Measure
  • Procedure

 

Bias that falsely identify or inflate risk factors

  • Recall
  • Observer
  • Interviewer
  • Misclassification
  • Random Misclassification
  • Channeling

 

Controlling for Bias

  • Design of Trial
    • Randomization
    • Selection Criteria
    • Blinding
    • Matching
    • Using Controls
  • Analysis

Controlled vs Non-Controlled

Various Types of Controls

  • Placebo
  • Historical
  • Crossover
  • Standard or Active Treatment
  • Within Patient Comparison

Blinding in Trial Design

Non-blinded

Single-blinded

Double-blinded

Double-dummy

Triple-blind

Total-blind

Note concerning trials that claim blinding, but may not be blinded.

Run-In-Phase

Confounding

Arrow Chart Examples

Co-linearity

Controlling for Confounding

  • Design of Trial
    • Randomization
    • Selection Criteria
    • Blinding
    • Matching
  • Analysis
    • Stratification
    • Multivariate Regression Analysis
    • Note concerning various types of ANOVA used

Validity

Internal

External

Prospective vs Retrospective

General Considerations for Assessing Causality

  • Relative strength of causal relationships

 

Retrospective Trials

  • Case-Control
    • Benefits
    • Problems
  • Cohorts
    • Retrospective Cohort
    • Prospective Cohort (retrospective)
    • True Prospective Cohort
    • Benefits
    • Problems

Odds Ratios, Relative Risks (aka Risk Ratios, Rate Ratio, or Incidence Rate Ratio)

Odds Ratio (see below for further explanation of examples)

Relative Risk (see below for further explanation of examples)

Hazard Ratio

Interpretation

Absolute Risk

Absolute Risk Reduction or Increase

Numbers Needed to Treat or Harm

Relative Risk Examples for RCTs and Cohort Trials

  • Example 1: Relative Risk Reduction example w/ Calculations and Interpretations
    • Absolute Risk
    • Absolute Risk Reduction
    • Numbers Needed to Treat
    • Relative Risk
    • Relative Risk Reduction
    • Difference vs Cohort Trial
  • Example 2: Relative Risk Increase example with Calculations and Interpretations
    • Absolute Risk
    • Absolute Risk Increase
    • Numbers Needed to Harm
    • Relative Risk
    • Relative Risk Increase
    • Difference vs Cohort Trial

 

Odds Ratio Examples for Case Control Trials

  • Example 1 w/ Calculations and Interpretation
  • Example 2 w/ Calculations and Interpretation
  • Note concerning change in Incidence's effect on estimation of Relative Risk

Randomized Controlled Trials

Parallel Design

Cross-over Design

Considerations

Disadvantages

Various Types of Analyses

Intention of Treat (ITT)

As Treated

Per Protocol

Post Hoc

Note concerning trials that claim to be ITT, but may not truly be ITT.

Run-In-Phase

Interim Analysis

Subgroup Analysis

Survival Analysis

  • Hazard
  • Life table
    • Actuarial Method
    • Kaplan-Meier
  • Statistical tests
    • Log-Rank
    • Wilcoxon-type
    • Cox Proportion Hazards

 

Meta-Analysis

Combined Endpoints

 

Miscellaneous

Breslow Day test

Rule of Four

Abbreviations

 

References

 

Index

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