2. Sampling and measurement

2. Sampling and measurement - 2. Sampling and Measurement...

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2. Sampling and Measurement Variable – a characteristic that can vary in value among subjects in a sample or a population. Types of variables Categorical (also called qualitative ) Quantitative (There are different statistical methods for each type)
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Categorical variable – scale for measurement is a set of categories Examples : Racial-ethnic group (white, black, Hispanic) Political party identification (Dem., Repub., Indep.) Vegetarian? (yes, no) Mental health evaluation (well, mild symptom formation, moderate symptom formation, impaired) Happiness (very happy, pretty happy, not too happy) Religious affiliation Major
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Quantitative variable – possible values differ in magnitude Examples: Age, height, weight, BMI = weight(kg)/[height(m)] 2 Annual income GPA Time spent on Internet yesterday Reaction time to a stimulus (e.g., cell phone while driving in experiment) Number of “life events” in past year
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Scales of measurement For categorical variables, two types: Nominal scale – unordered categories Preference for President, Race, Gender, Religious affiliation, Major Opinion items (favor vs. oppose, yes vs. no) Ordinal scale – ordered categories Political ideology (very liberal, liberal, moderate, conservative, very conservative) Anxiety, stress, self esteem (high, medium, low) Mental impairment (none, mild, moderate, severe) Government spending on environment (up, same, down)
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For quantitative variables, set of possible values is called an interval scale . (i.e., numerical interval between each possible pair of values)
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This note was uploaded on 07/12/2011 for the course STA 3030 taught by Professor Agresti during the Spring '11 term at University of Florida.

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2. Sampling and measurement - 2. Sampling and Measurement...

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