Unit 1: Exploring One-Variable Data (copy)

Categorical Variable

A variable that takes on category names or group labels.

Frequency Table

A table that gives the number of cases falling into each category.

Relative Frequency Table

A table that gives the proportion or percent of cases falling into each category.

Quantitative Variable

A variable that takes on numerical values for a measured or counted quantity.

Discrete Quantitative Variable

A variable that takes on a finite or countable number of values with "gaps" between each value.

Continuous Quantitative Variable

A variable that can take on uncountable or infinite values with no gaps.

Median

The middle number of a set of numbers arranged in numerical order.

Mean

The sum of items in a set divided by the number of items.

Standard Deviation

The square root of the variance, giving a typical distance that each value is from the mean.

Interquartile Range (IQR)

The difference between the upper quartile (Q3) and the lower quartile (Q1); the range of the middle 50%.

Skewed Distribution

A distribution that is not symmetrical, where values are spread unevenly.

Bimodal Distribution

A distribution with two distinct peaks.

Unimodal Distribution

A distribution with one peak.

Empirical Rule

A rule stating that for a normal distribution, about 68% of values lie within 1 standard deviation, 95% within 2 standard deviations, and 99.7% within 3 standard deviations of the mean.

Percentile Ranking

Indicates what percentage of all values fall at or below a specific value.

Z-score

Indicates how many standard deviations a particular value is from the mean.

Range

The difference between the largest and smallest values in a dataset.