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Week 2 Continued:

Variables

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Independent and Dependent Variables Independent variable

Variables that are thought to influence or explain variation in the dependent variable.

Experimental treatment or predictor variables.

Dependent variable Criterion or outcome variable.

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Examples of Independent Variables Teaching Method Diet Plan Medication Gender Age Treatment Condition Achievement Score

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Examples of Dependent Variables Attitudes Success in graduate school Homesickness of first year at college Success at controlling behavior Reduction of symptoms Achievement Score Time in 100 meter dash

*The independent and dependent variable depends on the research question being asked.

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Variable Name vs. Variable Values Variable name - properties of objects,

events, and people that can take on different values Hair color Gender Speed Goal orientation Self-esteem

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Variable Name vs. Variable Values Variable values: values of variable name

Variable Name Variable Value

Hair color Brown, blond, black, red

Gender/sex Male, female

Goal orientation Performance-approach, Mastery-approach

Speed MPH

Self-esteem Score on survey computed, low, medium, high

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Identifying IV and DV I want to determine if third grader’s math achievement

significantly increases due to the use of manipulatives.

Is there a significant difference in amount of students’ dazing during a lecture hour among the three different room arrangements?

Is there a significant difference in work productivity in a glue factory when working to a low tempo of music versus a high tempo of music?

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Identifying IV and DV Is there a significant difference in weight loss

between those on a diet and those exercising?

Does highest degree earned (GED, HS,college) affect social awareness?

Is there a significant difference in cognitive development among infants born less than 4 pounds, 4.1-6 pounds, and 6.1-8 pounds?

Do elementary school boys and girls differ in their needs for social interaction?

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Identifying IV and DV

A researcher has developed a new aid for teaching 7th grade students about electric circuits. The researcher wants to know whether students’ knowledge of electric circuits increases more using the aid if they

(a) explore it individually without instruction, (b) are given written instructions about it, or (c ) watch a demonstration of how it works. The researcher administers a pre- and post-test

to assess students’ learning.

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Identifying IV and DV’S

A company wants to investigate the influence of three types of training programs (coworker, consultant, self) on employees’ job performance three months after the programs have been completed.

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Categorical vs. Continuous Variables

Categorical variables Take on a small set of possible values Typically qualitative Also called “qualitative” or “discrete” variables Examples:

Variable Category

Gender Male, female

Political party Republican, Democrat, Independent

Ethnicity African American, White, Asian, Hispanic

Parenting style Passive, Authoritarian, Authoritative

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Discrete vs. Continuous Variables

Continuous variables Always quantitative Measurement Less to more of something Able to put on a continuum and quantify (assign meaningful #

to it) Examples:

Variable Scale (Less to more)

Age Years

Temperature FO or CO

Running time Minutes

Heart rate Beats per minute

Distance Miles, yards, meters

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Scales of Measurement Categorical Continuous

Nominal Ordinal Interval Ratio

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Scales of Measurement Nominal scale

Labels items; often meaningless No scale quality

Example: Male = 1 Female = 2 (dichotomous)

Example: Blue eyes = 1 Brown eyes = 2 Green eyes = 3

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Scales of Measurement Ordinal Scale

Orders people, objects, events along some continuumExamples:1. Who did better on a test (rank order)

2. Likert-type rating scales (1-4, 1-5, 1-7, etc.)

3. Age transformed

20-25 years = 126-30 years = 231-35 years = 336-40 years = 441-45 years = 546 years and older= 6

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Scales of Measurement Interval Scale

Intervals have the same interpretation throughout Example: Difference between 30 degrees and 40 degrees

represents the same temperature difference as the difference between 80 and 90 degrees.

Not perfect. No true zero point. 0 degrees Fahrenheit does not mean the complete absence of

temperature. Can’t compute ratio’s due to this fact.

40 degrees not one-half of 80. 80 degrees is not twice as hot as 40 degrees.

Because no true zero value!!

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Scale of Measurement Ratio scale

Most informative scale. Provides name or category for each object (numbers as labels). Objects are ordered (in terms of numbers). Same difference at two places on the scale has the same

meaning. Interval scale with zero position added.

So, can have absence of the quantity measured. Zero money (no money) Someone with 50 cents has twice as much money as

someone with 25 cents Age, height, weight, percentage

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Complete Assignment 1: Identifying Independent and Dependent Variable(s) and their Properties in a Research Question

Note cards: Sample vs. Population Descriptive vs. Inferential statistics Variable name vs. value Independent vs. dependent variable Types of variables (Dichotomous, Categorical,

Continuous) Scales of measurement (nominal, ordinal, interval, ratio)