Intro to Statistics

Flashcards covering key vocabulary terms and definitions from the lecture on Intro to Statistics, Measures of Central Tendency, and Measures of Variability.

Statistics

Tools for organizing, summarizing, and generalizing about data, and accounting for variability in real life.

Descriptive statistics

Methods to organize and summarize variability in a collection of actual observations or scores, making them concise and understandable.

Inferential statistics

Methods that allow generalization beyond actual observations, designed to help make decisions and test hypotheses.

Qualitative data

Words, letters, or numerical codes that represent a class or category.

Ranked data

Numbers that represent relative standing, placing things/people in order.

Quantitative data

Numbers that represent an amount or a count.

Nominal level of measurement

A level of measurement (with qualitative data) where numbers only help to distinguish one category from another (classification).

Ordinal level of measurement

A level of measurement (with ranked data) where numbers place things/people in order but provide no information on how far apart they are.

Interval/Ratio level of measurement

A level of measurement (with quantitative data) where numbers place objects/people in order with meaningful differences, and ratio data has a true zero point.

Distributions of Data

A representation of how often scores/values occur in data (frequency), showing both spread and differences in frequency.

Modality

A characteristic of distributions describing how many peaks are present.

Skewness

A characteristic of distributions describing whether the graph is symmetric or not.

Normal Distribution

A unimodal and symmetric distribution where the mode, median, and mean are equal.

Positive Skew

A distribution where the tail is to the right, and typically Mode < Median < Mean.

Negative Skew

A distribution where the tail is to the left, and typically Mean < Median < Mode.

Measures of Central Tendency

Statistics that describe the middle or typical value of a distribution (mode, median, mean).

Mode

The most frequently occurring number in a set of data, not affected by extreme values.

Median

The middle value in an ordered set of data, or the mean of the two central scores if the count is even, less susceptible to outliers.

Mean

The average of all scores in a data set, calculated by summing all scores and dividing by the number of scores, sensitive to extreme values.

Measures of Variability

Statistics that measure the amount by which scores are dispersed or scattered in a distribution.

Range

The difference between the largest and smallest scores in a data set, covering the whole spread of data.

Variance

The degree to which the scores differ on average (vary around) the mean, calculated as the mean of all squared deviations, but not in useful units.

Sum of squares (SS)

The sum of all the squared deviations from the mean.

Degrees of Freedom (df)

The number of values in a study that are free to vary, typically (n-1) when estimating population parameters from a sample to account for the loss of one piece of information (the mean).

Standard Deviation

A rough measure of the average amount by which scores deviate on either side of the mean; it is the square root of the variance, providing a measure of distance in useful units.