# Ch. 1 – PSY 360 Josephine Mack
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Statistics

Consists of a set of mathematical procedures for organizing, summarizing, and interpreting information. (research involves gathering information)
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Standardized Techniques

Statistics provides researchers with _____ that are recognized and understood throughout the scientific community *Ensures information and observations are presented and interpreted in an accurate way.*
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Scientific Research

____ typically begins with a general question about a specific group (or groups) of individuals.
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Population

Set of all individuals of interest in a particular study.
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Sample

Set of individuals selected from a population, usually intended to *represent the population* in a research study. – Used to make *inferences* about the characteristics of the population.
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Inference

Using information about one situation to make logical conclusions about some other situation.
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Generalized

Results from the sample are ____ to the population.
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Parameter

A value that describes a *population* (usually numerical) Single measurement May be derived from a set of measurements from the population.
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Statistic

A value that describes a *sample* (usually numerical) Single Measurement May be derived from a set of measurements from the sample
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Data

Measurements or observations
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Datum

A single measurement or observation (score or raw score)
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Data Set

Collection of measurements or observation
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Variables

Characteristics or conditions that *change* or have different values for different individuals. – *Individual characteristics* such as height, weight, gender, personality – *Environmental Conditions* Temperature, time of day, weather
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Observations/Take Measurements

In order to document relationship between variables, you have to make _________.
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Descriptive Statistics

Statistical procedures used to *summarize, organize, and simplify* data.
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Organize

Tables or graphs are used to _____ data
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Summarize

*Descriptive values* such as the average score, range, frequency, etc. are used to _____ data.
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Descriptive Value

A _____ for a population is called a parameter and for a sample is called a statistic
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Inferential Statistics

Technique that allows us to *study samples* and then *make generalizations* about the populations from which they were selected.
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Limited Information

Because a sample is typically only a part of the whole population, *sample data* provide only _____ about the population
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Imperfect Representatives

Sample statistics are generally ______ of the corresponding population parameters.
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Sampling Error

The discrepancy, or amount of error, that exists between a sample statistic and the corresponding population parameter.
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Defining and Measuring

_______ sampling error is a large part of *inferential statistics.*
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The Correlational Method

Goal is to determine whether there is a relationship between two variables and to describe the relationship. (time of day students wake up and academic performance) *Is there any consistent, predictable relationship between two variables?*
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Limitation of Correlational Method

It describes relationship, but *does not explain the cause and effect mechanism* of the relationship. We don’t know what factor(s) is responsible for late sleepers having lower grades.
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The Experimental Method

Goal is to establish a cause and effect relationship between two variables. Intended to show that *changes in one variable are caused by changes in another variable.*
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Characteristics of Experimental Method

– Researcher *manipulates one* of the variables and *observes* the *second* variable then determines *whether or not manipulation causes changes* to occur – Control over research situation. Do not want other, extraneous variables to influence the relationship between the variables.
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Environmental Variables

Variables inherent to the environment (time of day, weather, temp, lighting, etc.)
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Participant Variables

Variables inherent to individuals (gender, age, intelligence, height, etc)
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Confounded

If more than one variable can account for the results, the study is _______.
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Independent Variable (IV)

The variable that is manipulated by the experimenter. (should only be under influence of researcher)
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Treatment Condition

The different testing conditions or setting of the independent variable.
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Dependent Variable (DV)

Variable that is observed to asses a possible effect of the manipulation or treatment (should vary only as result of manipulation of the IV)
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Techniques to Control Variables

– Random assignment – Treatment conditions have to be identical except for the one manipulated variable. (Hold constant any other variable that might influence the DV)
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Random Assignment

– Each subject has an equal chance of being assigned to each of the treatment conditions. – Ensures that subjects in one treatment are not substantially different from the subjects in another treatment.
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Control Condition

Do not receive an experimental treatment. Either no treatment is administered or a placebo is administered. *Purpose:* Provide a baseline for comparison with the experimental condition.
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Experimental Condition

Receives the experimental treatment Independent variable must consist of at least two values (ex. money vs paper)
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Experimental Method

One Variable is manipulated while changes are observed in another variable. To establish a cause and effect relationship between two variables, an experiment attempts to eliminated or minimize the effect of all other variables.
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1 variable is measured; Both Variables are measured.

In an experimental method, ______ and in a correlational method, ______.
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Non-Experimental Method

Examines variable relationship by comparing groups of scores. *Cannot produce a cause/effect explanation* The researcher *does not have control* of the independent variable. (Quasi-IV) Ex. Gender
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Constructs

Internal attributes or characteristics that can’t be observed directly. Used to help *describe behavior.* EX. Intelligence, self esteem, anxiety, hunger.
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Operational Definition

Defines a construct in terms of external behaviors that can be observed and measured using a set of operations. *EX* Emotionality, IQ testing
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Emotionality

The amount of increase in heart rate after a person is insulted.
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Discrete Variables

Consists of separate, indivisible categories. No values can exist between two neighboring categories. *EX* numbers on a dice, amount of students in a class, gender, college major, occupation.
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Continuous Variable

An infinite number of possible values fall between any two observed values. Divisible into an infinite number of fractional parts. *EX* time, weight, height.
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Real Limits

The boundaries of intervals for scores that are represented on a continuous number line. The ____ *separating two adjacent scores* is located exactly *halfway between two scores* *Each score has two* Ex. Score 150 Upper: 150.5 Lower: 149.5
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Nominal Scale

Individuals are classified into categories that have different names. Measurements *label and categorize* observations, but *no quantitive distinction* is made between observations. Ex. academic major, gender, race. difference is determined, but the *direction or the size of the difference is not identified.*
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Ordinal Scale

Have different names, as in nominal scales, but are also *organized* in an *ordered sequence* (directional relationship) *Do not allow* you to *determine the size of the difference.* Observations are *ranked in terms of size or magnitude.* Ex. tshirt size: small, medium, large Results of race: first, second, third.
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Interval Scale

Consists of ordered categories (like ordinal scales) that are all intervals of exactly the same size. Can *identify the direction and size of differences* No absolute zero, zero is arbitrary. Ex. Temperature in Fahrenheit: zero degrees does not mean there is no temperature and does not prohibit the temp from going even lower.
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Ratio Scale

Similar to interval scale BUT *has an absolute zero point* meaning zero represents a complete absence of the variable being measured. Direction, size, and ratio of differences can be measured. Ex. 10 seconds is twice as much as 5. 6 feet is twice as long as 3 feet 200 pounds is twice as heavy as 100.
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Nature of the Zero Point

The *factor that differentiates* an interval scale from a ratio scale is the ________
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Statistical Notation

Represented by *X* (test scores) Two variables: *X and Y* (height and weight) *N* (number of scores in a *population*) *n* (number of scores in a *sample*)
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Sigma (greek letter)

Summation: \”the sum of\” Always followed by a symbol or mathematical expression *Identifies which values are to be summed* (Ex. sum of X: add all scores for variable X)
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Order of Operation

– *Parentheses* – *Exponents* – *Multiplying/Dividing* (L -> R) – *Summation* – *Subtraction* or any other summation
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Simplify and Summarize