BIOLOGY 200 - Biostatistics and Frequency Distributions

Vocabulary flashcards covering key statistical concepts, variables, graphical distributions, and descriptive metrics from BIOLOGY 200 notes.

Nominal Categorical Variable

A categorical variable in which the different categories have no inherent order.

Ordinal Categorical Variable

A categorical variable in which there is an order to the variables.

Sampling Error

The chance difference from the truth where estimates based on samples depart somewhat from the true population characteristics simply by chance.

Sample

A much smaller set of individuals selected from the population that a researcher uses to draw conclusions applying to the whole population.

Sample of Convenience

A collection of individuals that are easily available to the researcher, which is typically neither unbiased nor independent.

Normal Distribution

The familiar 'bell curve' and most important probability distribution in statistics, often used for continuous data to approximate the population probability distribution.

Scatter Plot

A graphical display of two numerical variables in which each observation is represented as a point on a graph with two axes.

Mode

The interval that corresponds to the highest peak in a histogram.

Uniform Histogram

A histogram that has no distinct peak.

Bimodal Histogram

A histogram that has two distinct peaks.

Symmetric Histogram

A bell-shaped histogram where the left and right side patterns are mirror images of each other.

Skewed Histogram

A histogram where the left and right side patterns do not mirror each other.

Box Plot

A graph that uses lines and a rectangular box to display the median, quartile, range, and extreme measurements of data.

Bar Graph

A display that uses the height of rectangular bars to visually show the frequency (or relative frequency) distribution of a categorical variable.

Frequency Table

A text display of the number of occurrences of each category in a data set.

Frequency Distribution

A display showing the number of observations for a particular measurement for a variable.

Relative Frequency

The proportion of observations having a given measurement, calculated as the frequency divided by the total number of observations.

Relative Frequency Distribution

The proportion (or fraction) of occurrences of each value of a variable in a data set.

Proportion

The most important descriptive statistic for a categorical variable, calculated by dividing the number of observations in the category of interest by $n$, the total number of observations in all categories combined.

Arithmetic Mean

The most common metric to describe the location of a frequency distribution, equivalent to the average of a set of measurements.

Quantile

A measure specifying the fraction of observations less than or equal to a given measurement.

Percentile

A measure specifying the percentage of observations less than or equal to a given measurement.

Coefficient of Variation

A statistic that calculates standard deviation as a percentage of the mean, represented by the formula $CV = \frac{s}{y} \times 100\%$.

Parameter

A quantity describing a population.

Estimate (Statistic)

A quantity calculated from a sample used to describe a population parameter.

Population

The entire collection of individual units that a researcher is interested in, typically composed of too many individuals to measure completely.

Statistical Hypothesis

A specific claim regarding a population parameter.

Random Sample

A sample in which each member of a population has an equal and independent chance of being selected.

Numerical Data

Quantitative measurements that have magnitude on a numerical scale, such as counts, dimensions, angles, rates, and percentages.

Strip Chart

A graphical display of a numerical variable and a categorical variable in which each observation is represented as a dot.

Mosaic Plot

A type of graphical display that uses the area of rectangles to display the relative frequency of occurrence of all combinations of two categorical variables, stacking the data on top of one another.

Summary Statistics

Quantities (also called descriptive statistics) that provide hard numbers capturing important features of frequency distributions.

Cumulative Relative Frequency

The fraction of observations less than or equal to a given measurement.

Precision

The inverse spread of estimates resulting from sampling error; lower sampling error leads to higher precision.

Bias

A systematic discrepancy between the estimates that would be obtained from repeated sampling and the true population characteristic.

Continuous Numerical Data

Numerical data that can take on an infinite number of any real-number values within a given range.

Discrete Numerical Data

Numerical data that come in indivisible units.

Map (Statistical Display)

The spatial equivalent of a line graph that uses a color gradient to display a numerical response variable across multiple locations on a surface.

Grouped Bar Graph

A graph using the heights of rectangles to plot the frequency of occurrence of all combinations of two or more categorical variables.

Line Graph

A type of graph that uses dots connected by line segments to display trends in a measurement over time or another ordered series.

Sum of Squares of Y

The summation term located in the numerator of the statistical formula for variance or deviation.