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    Haphazard Sampling: Selection Biases Induced by Control...
    research summary posted October 20, 2014 by Jennifer M Mueller-Phillips, tagged 08.0 Auditing Procedures – Nature, Timing and Extent, 08.02 Sample Selection – use of statistical sampling, 11.0 Audit Quality and Quality Control, 11.09 Evaluation of Evidence 
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    Title:
    Haphazard Sampling: Selection Biases Induced by Control Listing Properties and the Estimation Consequences of these Biases
    Practical Implications:

    These findings suggest that the properties of haphazard samples chosen from control listings are likely to differ from those of random samples.  Subconscious effort minimization and diversification behaviors, coupled with visual perception artifacts, yield samples that violate requirements for independence and equal selection probability.  These violations, in turn, are likely to produce biased error projections with difficult to discern risk properties.  Although widely used and specifically identified in audit standards as a sampling technique that can be employed to obtain a representative sample, haphazard sampling may not be a reliable substitute for random sampling.

     

    For more information on this study, please contact Thomas W. Hall

    Citation:

    Hall, T. W., A. W. Higson, B. J. Pierce, K. H. Price, and C. J. Skousen. 2012. Haphazard sampling: Selection biases induced by control listing properties and the estimation consequences of these biases. Behavioral Research in Accounting 24 (2):101-132.

    Keywords:
    nonstatistical sampling, haphazard sampling, sample selection bias
    Purpose of the Study:

    Audit samples represent an important type of evidence used to assess the error status of accounting populations.  As a result of its professional acceptance and lower cost, nonstatistical sampling historically has played a prominent role in audit sampling.  Haphazard sampling is a nonstatistical technique commonly used to emulate random sampling and consequently when used no explicit selection strategy should be employed.  However, a number of sampling experts have expressed doubts about whether haphazard sampling is a reliable substitute for random sampling.

     

    We hypothesized that haphazard samples differ from random samples because the haphazard selection process is influenced by: (1) auditor behaviors intended to minimize sample selection effort and to ensure a diversified sample composition, and (2) variations in the appearance of control listing entries.

    Design/Method/ Approach:

    We created two control listings representing a population of accounts receivable and a population of inventory items.  The accounts receivable control listing consisted of 22 pages with 792 customer accounts, while the inventory control listing consisted of 26 pages with 1,404 inventory items.

     

    We conducted three experiments in which participants were instructed to select haphazard samples from the control listings.  Participants in the first experiment were 75 students enrolled in either senior or master’s-level accounting courses at a public university located in the southwestern United States.  The second experiment utilized 40 university students in the United Kingdom who were enrolled in either senior or master’s-level accounting courses.  These students serve as effective proxies for entry-level auditors, who select most samples.  The third experiment utilized 53 audit seniors from two offices of a Big 4 audit firm located in the southwestern United States.  Because of time constraints, the audit seniors sampled only from the inventory control listing.  Upon completion of the sample selection process, all participants completed an exit survey.  The data collection was completed by the middle of 2009.

    Findings:

    As expected, we observed unequal page selection rates.  Most participants began the sample selection process on the first page of control listings.  Also, sample selections exhibited a high positive correlation with listing serial position, indicating that participants tended to proceed through the control listings in serial fashion.  Statistical analyses confirmed that participants exhibited higher selection rates for early pages, followed by declining selection rates for middle pages, with an upturn in selection rates for ending pages.  All of these results are inconsistent with the properties of random samples.

     

    Line selection rates also were unequal and consistent with expectations that visual perception biases influence sample selections.  Line entries with a low level of visual crowding tended to have higher selection rates than line entries with a high level of visual crowding.  Similarly, line entries with a high level of luminance contrast were selected more often than line entries with lower levels of luminance contrast.  Statistical tests confirmed that lines at the top and bottom of pages were overrepresented in each participant group’s samples. As with page selection, these results are inconsistent with the properties of random samples.

    Category:
    Audit Quality & Quality Control, Auditing Procedures - Nature - Timing and Extent
    Sub-category:
    Evaluation of Evidence, Sample Selection – use of statistical sampling