Descriptive Statistics & Graphing – Week 1 (Lecture 2)

Vocabulary flashcards summarising key terms, measures, and graphs from the lecture on descriptive statistics and data display.

Descriptive Statistics

Statistical techniques that summarize or describe the characteristics of a sample’s data without drawing conclusions about a wider population.

Inferential Statistics

Procedures that use sample data to make estimates, decisions, or predictions about a population.

Continuous Data

Numerical data that can take on any value within a range; measured on interval or ratio scales (e.g., height, test scores).

Categorical Data

Data sorted into distinct groups or categories; measured on nominal or ordinal scales (e.g., gender, course name).

Nominal Scale

Measurement scale that labels categories without any quantitative value or order (e.g., blood type).

Ordinal Scale

Measurement scale that ranks categories in a specific order but without equal intervals (e.g., Likert ratings).

Interval Scale

Numerical scale with equal intervals but no true zero point (e.g., temperature in °C).

Ratio Scale

Numerical scale with equal intervals and a true zero, allowing statements about how many times greater one value is than another (e.g., weight, income).

Central Tendency

A group of statistics (mean, median, mode) that locate the center or typical value of a distribution.

Dispersion (Variability)

Statistics (range, variance, SD, etc.) that show how spread out or clustered data values are.

Mean (Arithmetic Mean)

The average of a set of scores, found by summing all values and dividing by the number of observations.

Median

The middle value of an ordered data set; divides the distribution into two equal halves.

Mode

The most frequently occurring value or category in a data set.

Variance

The average of the squared deviations of each score from the mean; measures overall spread.

Standard Deviation (SD)

The square root of variance; the typical distance of scores from the mean.

Range

Simple measure of spread; the difference between the highest and lowest observed values.

Percent Distribution

A display of the percentage of cases falling into each category of a categorical variable.

Percentile

A value below which a given percentage of observations fall (e.g., 25th percentile).

Quartile

One of three points (Q1, Q2, Q3) that divide ordered data into four equal parts.

Interquartile Range (IQR)

The difference between the 75th and 25th percentiles; spans the middle 50 % of data.

Histogram

Graph for continuous data with adjacent bars (bins) representing frequency across equal intervals.

Bar Chart

Graph for categorical data with separated bars whose heights represent frequencies or percentages.

Pie Chart

Circular chart showing relative proportions of categories as slices of a whole.

Box Plot (Box-and-Whisker Plot)

Graph displaying the median, quartiles, potential outliers, and range of a distribution.

Stem-and-Leaf Plot

Tabular graph that shows actual data values split into stems and leaves while visualizing shape.

Frequency Polygon

Line graph created by connecting mid-points of histogram bins, showing distribution shape.

Skewness

Statistic indicating asymmetry of a distribution; positive skew has a long right tail, negative skew a long left tail.

Kurtosis

Statistic describing the ‘peakedness’ or flatness of a distribution relative to normal.

Standard Error (of Skewness/Kurtosis)

Expected sampling variability of a statistic across repeated samples from the same population.

Outlier

An observation markedly distant from other values; often flagged in box plots.

Symmetrical Distribution

A distribution in which left and right sides are mirror images (skewness ≈ 0).

Positively Skewed Distribution

Distribution with a long tail to the right; many low scores and few high scores.

Negatively Skewed Distribution

Distribution with a long tail to the left; many high scores and few low scores.

Sample

A subset of a population selected for study; basis for descriptive statistics.

Population

The entire group of individuals or observations of interest in a study.

Mu (μ)

Greek symbol representing the population mean in statistical notation.

SPSS

Statistical software package widely used to compute descriptive and inferential statistics.

Frequency Table

Tabulation listing each value of a variable and the number of times it occurs in the data.

Confidence Interval (CI)

Range of values, derived from sample statistics, that is believed to contain the population parameter with a specified probability (e.g., 95 %).