Statistics VOcab Study Guide

Sample Survey

Data collected from a sample to estimate population characteristics.

Census

Data collected from every member of the population.

Sampling Error

Differences between the sample result and the actual population value.

Non-Sampling Error

Errors from poor sampling methods, data entry mistakes, or bias.

Sampling with Replacement

Selected individuals are put back into the population before the next selection.

Sampling without Replacement

Selected individuals are not returned to the population after selection.

Raw Data:

Unorganized and unprocessed data collected directly from observations.

Histogram

A graph using bars to represent frequency of intervals (used for quantitative data).

Line Graph

Shows trends over time or ordered data points.

Bar Graph

Uses bars to show frequency of categorical data (used for qualitative data).

Frequency Distribution

A table that shows how often each data value or range occurs.

Relative Frequency

Proportion of the total for each class (frequency÷total)(frequency ÷ total)(frequency÷total).

Relative Frequency Percent

Relative frequency expressed as a percent.

Cumulative Frequency

The running total of frequencies through the classes.

Left-Skewed Distribution

Data tails off to the left; mean < median

Right-Skewed Distribution

Data tails off to the right; mean > median

Uniform Distribution

All values have roughly the same frequency.

Symmetric Distribution

Left and right sides of the graph mirror each other.

Percentile Rank

The percent of values below a certain value.

Measure of Location

Describes the position of a value in the data set.

Percentile

Value below which a given percent of data falls

Quartile

Divides data into four equal parts (Q1 = 25%, Q2 = 50%, Q3 = 75%).

Measure of Central Tendency

Describes the center or average of a data set

Mean

Average (sumofvalues÷numberofvalues)

Median

Middle value when data is ordered

Mode

Value(s) that appear most frequently

Range

Difference between the highest and lowest values

Variance

Average of squared differences from the mean.

Standard Deviation

Square root of the variance

Coefficient of Variation

Standard deviation divided by the mean, used to compare spread across different units.

Outlier

A value significantly higher or lower than the rest of the data