COM 633: Content AnalysisSampling and Units

Kimberly A. Neuendorf, Ph.D.

Cleveland State UniversityFall 2010

Defining the PopulationResearcher 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 & SamplePopulation 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

UnitsWeyls (2001); study of adult entertainment

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

Unit of sampling

Unit of data collection

Unit of analysis

UnitsWeyls (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

UnitsWeyls (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

UnitizingUnit—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

ArchivesUnprecedented access to “archives” online!Comprehensive vs. SelectiveElectronic/online vs. nonFree vs. costly

Medium ManagementArchiving messagesSearching for messagesPreparation of messages for coding/handling during codingAutomated content analysis

Medium ManagementA changing area. . . More later in the term

SamplingRandom or Probability Sampling

Simple random sampling (SRS)Systematic sampling---------------------------------Cluster samplingStratified samplingMultistage sampling

SamplingNon-probability (nonrandom) Sampling

Convenience samplingPurposive or judgment samplingQuota sampling

Sample SizeRules of thumb

At least 100A “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)