Fundamentals of Biostatistics: Understanding Research Questions and Data Analysis
Learn about bias, types of data, hypothesis testing, correlations, and more in biostatistics with an emphasis on research questions and data analysis methodologies.
Fundamentals of Biostatistics: Understanding Research Questions and Data Analysis
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Presentation Transcript
Basic Biostatistics Prof Paul Rheeder Division of Clinical Epidemiology
Overview • Bias vs chance • Types of data • Descriptive statistics • Histograms and boxplots • Inferential statistics • Hypothesis testing: P and CI • Comparing groups • Correlation and regression
Research Questions? • Does CK level predict in hospital mortality post MI? • Is there an association between troponin I and renal function? • What is the Incidence of amputation in diabetics with renal failure? HOW ARE THEY MEASURED???
Research question • Does aspirin reduce CV mortality in diabetics when used for primary prevention? • Is there an increased risk between cell phone use and brain cancer? • Does level of SES correlate with depression?
Research question • So your research question must be phrased in such a manner that you can answer YES or NO or provide some quantification of sorts.
Data analysis • Aim: to provide information on the study sample and to answer the research question !
Problems • Bias and confounding also called systematic error…. Typically dealt with in the planning and execution of the study…can also control for it in the data analysis (eg multivariate analysis) • Chance also called random error. Classically P values (and CI) can be used to judge role of chance
First important issues • What type of data are you collecting • Typically one has some outcome variable and some exposure variable or variables? • How and with what are they measured?
Outcome and exposure? • Does CK level predict in hospital mortality post MI? • Is there an association between troponin I and renal function? • What is the Incidence of amputation in diabetics with renal failure? HOW ARE THEY MEASURED???
Research question • Does aspirin reduce CV mortality in diabetics when used for primary prevention? • Is there an increased risk between cell phone use and brain cancer? • Does level of SES correlate with depression?
Research question • So your research question must be phrased in such a manner that you can answer YES or NO or provide some quantification of sorts.
Types of data • Categorical: HT yes or no, sex, smoking status (usually a %) • Ordinal versus nominal • Continuous data • Spread of continuous data
Data analysis • Descriptive stats • Mean/median • SD or range
Hypothesis testing • Differences between groups: • Examples: • T test/Mann Whitney (2 groups) • ANOVA/ Kruskal Wallis (>2 groups) • Chi square if it is %
Associations between variables • Does coffee cause cancer (OR, RR) • Efficacy of Rx (RRR, ARR, NNT) • If BMI associated with BP (correlation and regression)
2 X 2 table RR= (a/a+b)/(c/c+d) OR = (a/b)/(c/d)
Mean ± 1.96 SD = 95% range of sample • Mean ± 1.96 SEM=95% Confidence interval
