Psychological Statistics Exam 1 (Chapters 1-4)

Questions and Answers

What is the definition of statistics?

A type of psychological analysis

A method for scientific experimentation

A means of collecting qualitative data

A branch of mathematics used to summarize, analyze, and interpret data (correct)

What is the plural form of a single measurement or observation?

Data

Define descriptive statistics.

Procedures used to summarize, organize, and make sense of a set of scores or observations.

What is inferential statistics used for?

To infer or generalize observations made with samples to the larger population. Signup and view all the answers

What is the population in statistical terms?

The set of all individuals, items, or data of interest. Signup and view all the answers

What is a population parameter?

A characteristic that describes a population. Signup and view all the answers

What is the definition of a sample?

A set of individuals, items, or data selected from a population. Signup and view all the answers

Define a sample statistic.

A characteristic that describes a sample. Signup and view all the answers

What is science defined as?

The study of phenomena through strict observation and evaluation Signup and view all the answers

What are the elements of control in an experiment?

Manipulation, randomization, and comparison/control. Signup and view all the answers

What is random assignment?

A procedure that ensures participants have an equal chance of being assigned to a group. Signup and view all the answers

What is the independent variable?

The variable manipulated in an experiment. Signup and view all the answers

What is the dependent variable?

The variable that is measured in each group of a study. Signup and view all the answers

Define operational definition.

A description of observable events in terms of how they were measured. Signup and view all the answers

What is a quasi-independent variable?

A preexisting variable that differentiates groups in a study. Signup and view all the answers

What are scales of measurement?

Rules for how the properties of numbers can change with different uses. Signup and view all the answers

What are nominal scales?

Measurements where a number is assigned to represent something or someone. Signup and view all the answers

Define ordinal scales.

Measurements that convey order or rank. Signup and view all the answers

What are interval scales?

Measurements that have no true zero and are distributed in equal units. Signup and view all the answers

Define true zero.

A value of 0 that truly indicates nothing on a measurement scale. Signup and view all the answers

What is a continuous variable?

Measured along a continuum at any point beyond the decimal. Signup and view all the answers

Define discrete variable.

Measured in whole units or categories not distributed along a continuum. Signup and view all the answers

What is a quantitative variable?

Varies by amount and is measured numerically. Signup and view all the answers

Define qualitative variable.

Varies by class and is represented as a label. Signup and view all the answers

What is frequency in statistics?

The number of times a category or score occurs. Signup and view all the answers

What is a frequency distribution?

A summary display for a distribution of data organized by how often scores occur. Signup and view all the answers

Define simple frequency distribution.

Displays the frequency of each individual score or category in a distribution. Signup and view all the answers

What is grouped data?

Scores distributed into intervals where frequencies fall into given intervals. Signup and view all the answers

Define interval.

A discrete range of values within which frequency is contained. Signup and view all the answers

What is the real range in a data set?

One more than the difference between the largest and smallest value. Signup and view all the answers

What is interval width?

Range of values contained in each interval of a grouped frequency distribution. Signup and view all the answers

Define interval boundaries.

Upper and lower limits for each interval in a grouped frequency distribution. Signup and view all the answers

What is a lower boundary?

Smallest value in each interval of a frequency distribution. Signup and view all the answers

What is an upper boundary?

Largest value in each interval of a frequency distribution. Signup and view all the answers

Define open interval.

An interval with no defined upper or lower boundary. Signup and view all the answers

What are outliers in statistics?

Extreme scores that fall substantially above or below most scores in a dataset. Signup and view all the answers

What is cumulative frequency distribution?

A summary display that distributes the sum of frequencies across intervals. Signup and view all the answers

Define relative frequency distribution.

Summary display that distributes the proportion of scores in each interval. Signup and view all the answers

What is a proportion in statistics?

A part of all measured data; the sum of all proportions equals 1.0. Signup and view all the answers

Define relative percent distribution.

Summary display that distributes the percentage of scores in each interval. Signup and view all the answers

What is cumulative relative frequency distribution?

Summary display that distributes the sum of relative frequencies across intervals. Signup and view all the answers

Define cumulative percent distribution.

Summary display that distributes the sum of relative percents across intervals. Signup and view all the answers

What is a percentile point?

Value of a score below which a specified percentage of scores fall. Signup and view all the answers

What is a percentile rank?

Percentage of scores with values that fall below a specified score. Signup and view all the answers

Define ungrouped data.

A set of individual scores or categories where frequency is counted. Signup and view all the answers

What is a histogram?

Graphical display summarizing frequency of continuous data in intervals. Signup and view all the answers

Define frequency polygon.

A dot-and-line graph used to summarize frequency of continuous data. Signup and view all the answers

What is an ogive?

A dot-and-line graph summarizing cumulative percent of continuous data. Signup and view all the answers

Define bar chart.

Graphical display summarizing frequency of discrete and categorical data. Signup and view all the answers

What is a pie chart?

Graphical display in the shape of a circle summarizing relative percent of data. Signup and view all the answers

Define sector in a pie chart.

Particular portion representing the relative percent of a category. Signup and view all the answers

What is central tendency?

Statistical measures locating a single representative score. Signup and view all the answers

Define population size.

Number of individuals constituting an entire population. Signup and view all the answers

What is sample size?

Number of individuals constituting a subset from a larger population. Signup and view all the answers

Define mean.

Sum of scores divided by the total number of scores. Signup and view all the answers

What is population mean?

Mean for a set of scores in an entire population. Signup and view all the answers

Define sample mean.

Mean calculated for a sample. Signup and view all the answers

What is a weighted mean?

Combined mean of two or more groups of scores with unequal numbers. Signup and view all the answers

Define median.

Middle value in a distribution of data listed in order. Signup and view all the answers

What is mode?

Value in a dataset that occurs most frequently. Signup and view all the answers

Define normal distribution.

A symmetrical distribution where scores are evenly distributed around the mean. Signup and view all the answers

What is a skewed distribution?

A distribution of scores with outliers that fall outside of the main data range. Signup and view all the answers

Define positively skewed distribution.

A distribution with outliers that are significantly larger. Signup and view all the answers

What is a negatively skewed distribution?

A distribution with outliers that are significantly smaller. Signup and view all the answers

Define modal distribution.

A distribution in which one or more scores occur most frequently. Signup and view all the answers

What is unidimensional or unimodal distribution?

A distribution where one score occurs most often. Signup and view all the answers

Define bimodal distribution.

A distribution where two scores occur most frequently. Signup and view all the answers

What is multimodal distribution?

A distribution where more than two scores occur most frequently. Signup and view all the answers

Define nonmodal distribution.

A distribution where all scores occur at the same frequency. Signup and view all the answers

What is variability in statistics?

A measure of the dispersion of scores in a distribution. Signup and view all the answers

Define range.

Difference between the largest and smallest values in a dataset. Signup and view all the answers

What is interquartile range (IQR)?

Range of values between the upper and lower quartiles. Signup and view all the answers

Define semi-interquartile range (SIQR).

Half the distance between the upper and lower quartiles. Signup and view all the answers

What is variance?

A measure of the average squared distance scores deviate from their mean. Signup and view all the answers

What is population variance?

A measure of variability for a population's average distance from the mean. Signup and view all the answers

Define deviation.

Difference of each score from its mean. Signup and view all the answers

What is sum of squares (SS)?

The sum of the squared deviations of scores from their mean. Signup and view all the answers

What is sample variance?

A measure of variability for the average squared distance in a sample. Signup and view all the answers

Define biased estimator.

A sample statistic that does not equal its respective population parameter. Signup and view all the answers

What is an unbiased estimator?

A sample statistic that approximately equals its respective population parameter. Signup and view all the answers

What are degrees of freedom for sample variance?

The number of scores in a sample that are free to vary, n-1. Signup and view all the answers

Define definitional formula for variance.

A way to calculate variance by summing squared differences from the mean. Signup and view all the answers

What is computational formula for variance?

A formula that calculates variance without requiring squared differences. Signup and view all the answers

Define standard deviation.

A measure of variability representing average distance from the mean. Signup and view all the answers

What is population standard deviation?

A measure of variability for the average distance in a population. Signup and view all the answers

What is sample standard deviation?

A measure of variability for the average distance in a sample. Signup and view all the answers

What does the empirical rule state?

For normally distributed data, 99.7% lie within three standard deviations. Signup and view all the answers

What is Chebyshev's theorem?

Defines the percentage of data within standard deviations from any distribution. Signup and view all the answers

Study Notes

Statistics Fundamentals

Statistics involves summarizing, analyzing, and interpreting a set of numbers or observations.
Data refers to measurements or observations, with a plural form encompassing multiple scores.

Types of Statistics

Descriptive Statistics organize and present data through graphical, tabular, or summary forms.
Inferential Statistics enable generalization from sample observations to a broader population.

Populations and Samples

A population includes all individuals or items of interest, while a sample is a subset drawn from that population.
Population parameters are characteristics that describe a whole population, whereas sample statistics do so for a sample.

Research Methodology

Science is the systematic study of phenomena through observation and interpretation.
The Scientific Method comprises organized techniques for gathering and processing observable data.

Experimental Design

Experiments involve controlling conditions to determine cause-and-effect relationships between variables.
Random assignment helps ensure equal chances for participants to be placed in different study groups.

Variables in Research

Independent variables are manipulated, while dependent variables are measured and expected to change due to the independent variable.
Operational definitions detail how variables are observed or measured.

Measurement Scales

Scales of Measurement set rules for numerical properties, including nominal (categorizing), ordinal (ordering), and interval (equal units without a true zero).

Data Distribution and Display

Frequency denotes how often scores or categories occur; frequency distributions summarize this occurrence.
Histograms and frequency polygons visually display data distributions across intervals.

Measures of Central Tendency

Central Tendency identifies a score that is most descriptive of data: mean (average), median (middle), and mode (most frequent).
Normal distribution features symmetric distribution of scores around the mean.

Variability in Data

Variability assesses the spread of scores, calculated using range, interquartile range, variance, and standard deviation.
The range reflects the difference between the highest and lowest values; interquartile range focuses on the middle 50% of data.

Standard Deviation and Its Importance

Standard deviation measures how scores deviate from the mean, indicating data spread.
Empirical Rule states that a normal distribution features 68% of data within one standard deviation, 95% within two, and 99.7% within three.

Estimation in Statistics

Biased estimators may not accurately reflect population parameters, while unbiased estimators do on average.
Degrees of Freedom (df) indicate the number of scores in a sample free to vary.

Theorems and Theoretical Applications

Chebyshev's Theorem provides a percentage of data within any number of standard deviations, applicable regardless of distribution shape.

Summary of Key Terms and Definitions

Variance quantifies how far data points deviate from the mean.
Outliers are extreme values significantly different from the rest of the data.
Cumulative frequency distributions sum frequencies across intervals, providing a comprehensive view of data.

These notes encapsulate the core concepts from Chapters 1-4 of Psychological Statistics, covering definitions, types, and applications in the field.

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Test your knowledge with flashcards covering key concepts from Psychological Statistics Chapters 1-4. This quiz includes essential terms and definitions that are fundamental to understanding statistical analysis in psychology. Perfect for reviewing before the exam!