Biostatisitics Chapter 4

Biostatistics

Statistical methods to biological, medical and public health data

Nominal Variable

Labels, no order ex. Yes/No

Ordinal Variables

More than 2 responses; responses are ordered/ranked

Dichotomous- binary

Only 2 categories

Categorical Variables

Nominal

Ordinal

Dichotomous

Numerical Variables

Continuous

Continuous Variable

Assume any value between a theoretical; max and min

Types of continuous variables

Interval: an equal, quantitative interval between #

Ratio: equal intervals between them but have a meaningful 0

Mean

Average

All values added and divided by how many

Median

The middle of the data set

Mode

Most frequent occurring value

Range

Max-Min

Interquartile Range

Spread of the middle 50%

1st 25%

2nd 50%

3rd 75%

4th 100%

Relative Risk

Compares risk between two groups; exposed and unexposed

Odds ration

Case control studies

Term : Variable

Mode : Nominal

Median : Ordinal

Mean : continuous

Statistics vs Parameter

S: a numerical value calculated from a sample

P: a numerical Value that describes an entire population

Histograms

Used on continuous data. Longitudinal

Bar Graph

Categorical Data; separate bars to show categories compared to one another

Standard deviation

Measure of dispersion