Content Analysis:Sampling & Units

Kimberly A. Neuendorf, Ph.D.Cleveland State University

Fall 2011

Defining the Population Researcher fiat!? Let’s discuss. “The set of units to which the researcher

wishes to generalize.” Is a full sampling frame available? (e.g.,

population may be defined by a NEXIS search)

Population & Sample

Population Sample

The study of its units Census Survey, experiment, or content analysis

The number of units N n

A summary number about a variable and its distribution

Parameter Statistic

The mean of a variable µ M or X-bar

The standard deviation of a variable

σ sd

The variance of a variable

σ2 sd2

Units

Weyls (2001); study of adult entertainment

Lombard et al. (1996); study of TV production techniques

Unit of sampling

Unit of data collection

Unit of analysis

Units

Weyls (2001); study of adult entertainment

Lombard et al. (1996); study of TV production techniques

Unit of sampling

News story

Unit of data collection

News story

Unit of analysis Year

Units

Weyls (2001); study of adult entertainment

Lombard et al. (1996); study of TV production techniques

Unit of sampling

News story Time, date, channel

Unit of data collection

News story Episode, time interval, etc.

Unit of analysis Year Episode, time interval, etc.

UnitsNational Cancer Institutes (2003); study of news about mammography

Janstova (2006); study of films by Jane Campion vs. others

Unit of sampling

Unit of data collection

Unit of analysis

UnitsNational Cancer Institutes (2003); study of news about mammography

Janstova (2006); study of films by Jane Campion vs. others

Unit of sampling

News story

Unit of data collection

Story, attribution

Unit of analysis

News story

UnitsNational Cancer Institutes (2003); study of news about mammography

Janstova (2006); study of films by Jane Campion vs. others

Unit of sampling

News story Film

Unit of data collection

Story, attribution Film, character, 5-min. interval

Unit of analysis

News story Film, character, 5-min. interval

Unitizing

Unit—one decision rule might be to select the “smallest identifiable unit for which one can reliably code for the desired variables, thus providing maximal variance for these measures across the entire unit of sampling” (p. 72)

Coder unitizing vs. a priori unitizing Unitizing reliability is necessary when coders unitize BUT—How to assess unitizing reliability?

Krippendorff (2004) has begun to look at this

Sampling Random or Probability Sampling

“Every element in the population has an equal (or known) chance of selection”

Basic types: Simple random sampling (SRS) Systematic sampling

Variations on these types: Cluster sampling Stratified sampling Multistage sampling

Sampling Non-probability (nonrandom) Sampling

Convenience sampling Purposive or judgment sampling Quota sampling

Sample Size Rules of thumb

At least 100 A “rich range” on the variables of interest

Can use desired confidence interval to set sample size (but many formulae—Riffe, Lacy and colleagues have provided some examples)

pause