Biostats

Data

raw numerical terms: measurement, counting

Individual

a single entity or object

Variable

a characteristic that varies among individuals

Types of Variables

Quantitative and Qualitative

Quantitative Data

measurable amounts, numeric, mathematical computations, subtype: continuous

Qualitative Data

attributes or categories, descriptive, non-numeric, subtype: ordinal

Random Variable (RV)

unpredictable values arise from chance

Discrete RV

whole number values with gaps between them

Continuous RV

take any value within given range, no gaps

Population

entire group of interest

Sample

subset of the population used for analysis

Statistical Inference

procedure by which we reach a conclusion about a population on the basis of the information contained in a sample that has been drawn from that population

Research Study

a scientific study of a phenomenon of interest, design sampling products, collect and analyze data, provide valid conclusions based on results

Descriptive Study

describes the characteristics

Analytical Study

establishes casual relationships

Study Designs

the blueprint or framework for conducting the research study

Key Components of Study Designs

research question, population and sampling method, data collection procedures, variable and measurement tools, analysis plan

Types of Analytical Study

Observational and Experimental

Observational studies

non manipulation, support correlation findings

Experimental studies

manipulation of variables to observe effects, allow casual interference

Frequency Tables

a structured way to organize data that shows how often each value or range of values occurs

Purpose of grouping data

to summarize large datasets for easier understanding and visualization

Types of Frequency Tables

Frequency, Cumulative Frequency, Relative Frequency, Cumulative Relative Frequency

Frequency

lists the numbers of observations within each interval

Cumulative Frequency

sum of frequencies across contiguous intervals; useful for finding total number or proportion of values up to a certain point

Relative Frequency

the proportion of values in a class interval; calculated by dividing interval frequency by total observations

Cumulative Relative Frequency

sum of relative frequencies across contiguous class intervals; useful for identifying the proportion of values across two or more contiguous class intervals

Measures of Variability

described how spread-out data values are

Range

difference between max and min values in a dataset

Variance

average of squared deviations from the mean

Standard Deviation

square root of variance, most common measure of dispersion, keeps original units

Coefficient of Variation (CV)

relative variation, expresses the standard deviation as a percentage of the mean, useful for comparing datasets with different units or scales

Interquartile Range (IQR)

middle 50% spread, less sensitive to outliers than range