Psychological Statistics and Research Methods Vocabulary

Comprehensive vocabulary flashcards covering descriptive and inferential statistics, sampling methods, measurement scales, distributions, variability, research design, and survey methodology based on lecture notes and supplemental readings.

Statistics

How to quantitatively summarize data and make inferences from the data.

Population

The total collection of things (e.g., people, trees, etc.) that we seek information about.

Sample

A representative collection of those things drawn from the population.

Inference

The process of drawing conclusions about population parameters based on a sample taken from the population.

Point estimate

A single value derived from the sample (descriptive statistic) that can be used to estimate population value.

Confidence interval (CI)

Helps us express a point estimate as a range of a "best bet" where the true population parameter lies with repeated sampling.

Variable view

Lists a variable and its characteristics.

Data view

Lists observations and values for our variables.

Exclusive

Each item fits in no more than one bin.

Equal-sized

Each bin has the same range.

Exhaustive

Every item fits in a bin.

Normal distribution

A symmetrical distribution of data with a single peak and a bell shape.

Skewed distribution

Have many observations clumped on one end, with a "tail" of extreme values on the other (skewed) end.

Central tendency

A single number that describes the center or typical point of a distribution.

Mode

The most common value of the variable.

Median

The middle value in a frequency distribution.

Mean

The arithmetic average of all values for a variable.

Variability

How spread out a distribution is, aka how different [people] are from each other.

Between-subject

People differ from each other.

Within-subject

Same person fluctuates over time.

Random

Adding error to true reading randomly.

Systematic

Adding error to true reading consistently in one direction.

Range

A measure of variability that says how wide the distribution is.

Absolute range

Tells us the difference between the smallest and largest observed value.

Interquartile range (IQR)

The range of the middle $50\%$ of values; the values between the $25^{\text{th}}$ (Q1) and $75^{\text{th}}$ (Q3) percentile.

Mean absolute deviation (M.A.D)

Quantifies the mean of the absolute deviation.

Sum of squares

Summarizes amount of deviation from mean.

Population Variance

Average deviation from the mean in squared units.

Sample Variance

Average deviation from the mean in squared units, but now need to account for it being an estimate.

Degrees of freedom

The number of values that are free to vary in a sample used to estimate a population score.

Standard deviation

Average amount by which scores deviate from the mean in original units.

Histogram

A graph showing how many of the cases in a batch of data scored each possible value or range of values on a continuous variable.

Bar graph/chart

A graph representing categorical data, where the height of the bar is proportional to the value it represents.

Dot plot

Displays individual data points as a dot along a number line or axis.

z-score

A measure of how far from the mean a single data point is in units of standard deviations (rather than in units of the original variable).

Standard normal curve

A theoretical normal distribution with a mean of $0$ and a SD of $1$.

Column B

Proportion of data between the mean and the z-score.

Column C

Proportion of data beyond the z-score.

Surveys (or polls)

A method of gathering information from participants via self report.

Open-ended questions

Allows the participant to fill in the response in any way they like.

Forced-choice questions

The participant is given a limited set of options and must choose one.

Likert scales (or Likert-type scales)

Provide a range of forced-choice responses that are ratings.

Leading questions

Type of question in a survey/poll that's wording encourages only one response.

Double-barreled questions

Type of question in survey/poll that asks two or more questions in one.

Negatively worded questions

Type of question in survey/poll that contains negatively phrased statements, making its wording complicated or confusing.

Response sets

When participants give consistent responses across questions to save time, rather than accurately answering each question.

Fence sitting

When participants are hesitant to choose extreme answers and always opt for neutral responses.

Social desirability biases

Participants may respond in a way they think is socially desirable.

Observational research

A researcher watches or monitors participants (people or animals) and systematically records their behavior.

Naturalistic

Observation "in the wild".

Controlled

Observation in controlled setting such as lab.

Participant

Experimenter interacts with participants.

Observer bias

Observers have inherent biases that can affect interpretation of data.

Observer effects

Participants change behavior to match observers' expectations/behavior.

Reactivity

Participants may act differently if they know they are being observed.

Continuous Variables

Numerical variables that can take on any value in a certain range. Time and distance are continuous; gender, SAT score, and "time rounded to the nearest second" are not.

Control Group

The group in an experimental study that is not receiving the treatment being tested.

Convenience Sampling

Shortcuts to quickly gather data and get a general idea of how things work before fully investing a lot of time and money into well-designed research projects with proper sampling.

Data

The measured value of the variable.

Dependent Variable

The variable that is affected.

Descriptive Statistic

A set of statistics—such as the mean, standard deviation, and skew—that describe a distribution.

Discrete Variables

A variable that exists in indivisible units. For quantitative variables, it is measured in whole numbers that are discrete points on the scale.

Experimental Research

Research that involves the use of random assignment to treatment conditions and manipulation of the independent variable.

Independent Variable

The variable that is being manipulated.

Inferential Statistics

The branch of statistics concerned with drawing conclusions about a population from a sample.

Interval Scale

A numerical scale in which intervals have the same interpretation throughout.

Nominal Scale

Names or categorizes responses.

Non-experimental Research

Observing things as they occur naturally and recording our observations as data.

Ordinal Scale

Allows a comparison of the degree to which two subjects possess the dependent variable.

Qualitative Variables

Variables that express a qualitative attribute such as hair color, eye color, religion, favorite movie, gender, and so on.

Quantitative Variables

Variables that are measured in terms of numbers.

Quasi-experimental Research

Getting as close as possible to the conditions of a true experiment when we cannot meet all requirements.

Ratio Scale

An interval scale with the additional property that its zero position indicates the absence of the quantity being measured.

Sampling Bias

Our conclusions apply only to our sample and are not generalizable to the full population.

Sampling Error

A discrepancy between the parameter and the statistic we use to estimate it.

Simple Random Sampling

Every member of the population to have an equal chance of being selected into the sample.

Stratified Random Sampling

Used to make the sample more representative of the population.

Variable

A characteristic or feature of the thing we are interested in understanding.

Bell Curve

A normal distribution that has a single peak, known as the center, and two tails that extend out equally, forming what is known as a bell shape.

Bimodal Distribution

A distribution that has two peaks that lie roughly symmetrically on either side of the center point.

Bin Widths

The size of the interval represented by each bar in a histogram.

Box Plots

A standard graph in descriptive statistics that shows the shape, central tendency, and spread of numerical data.

Categorical Variables

A data type that places observations into distinct groups, labels, or categories rather than measuring them with numbers.

Frequency Polygons

A graphical device for understanding the shapes of distributions.

Lie Factor

Refers to the ratio of the size of the effect shown in a graph to the size of the effect shown in the data.

Skew

One of the two tails of the distribution is disproportionately longer than the other.

Stem-and-leaf Display

A graphical data tool that organizes numerical information by splitting each data point into a leading digit (the stem) and a trailing digit (the leaf).

Whiskers

Vertical lines that end in a horizontal stroke.

Arithmetic Mean

The sum of the numbers divided by the number of numbers.

Robustness

A term used by statisticians to mean resilience or resistance to outliers.

Area in the tails of the distribution

The probability or proportion of data located at the extreme left or right ends of a probability density curve, lying far from the mean.

Area under the curve

The region enclosed by a function's graph, an axis, and two boundary limits.

Scale

How far apart the scores are (their spread) and where they are located (their central tendency).

Standardization

Any normal distribution can be converted into a standard normal distribution by converting all of the scores in the distribution into z scores.

Standard Normal Distribution

A special, symmetrical bell-shaped probability distribution with a mean ($\mu$) of $0$ and a standard deviation ($\sigma$) of $1$.

Semantic differential format

A survey question format using a response scale whose numbers are anchored with contrasting adjectives.

Acquiescence

Answering "yes" or "strongly agree" to every item in a survey or interview. Also called yea-saying.

Socially desirable responding

Giving answers on a survey (or other self-report measure) that make one look better than one really is. Also called faking good.

Faking bad

Giving answers on a survey (or other self-report measure) that make one look worse than one really is.