Benford analysis counts the number of times each leading digit or digit combination occurs in a field, and compares the actual count to the expected count. The expected count is calculated using the Benford formula.

• You can analyze up to six leading digits. When analyzing four or more leading digits, Benford analysis output must be sent to a file instead of displayed on screen or sent to a printer.

• Depending on the number of records you are working with, analyzing five or more leading digits may take several minutes. Regardless of how many digits you are analyzing, you can press Esc to terminate the command at any time.

• Effective Benford analysis requires large data sets. ACL displays a warning in the results output when a data set may be too small for the specified number of digits.

• Anomalous data is more apparent when you analyze positive and negative values separately. You can use a filter to separate the two before beginning your analysis.

• Records with values of zero are ignored, but the number of zero-value records bypassed is reported. Leading zeros, numeric formatting such as decimals and dollar signs, other non-numeric digits, and records that fail to meet test criteria are also ignored. If the resulting number of digits is less than specified, ACL adds zeros to the right of the result.

Benford analysis output includes the following results:

• Leading Digits – Displays the leading digits that were tested. For example, if you specify one leading digit, the numbers 1 to 9 are displayed. If you specify two leading digits, the numbers 10 to 99 are displayed.

• Actual Count – Displays the count of each leading digit or leading digit combination found in the field.

• Expected Count – Displays the expected count of each leading digit or leading digit combination calculated by the Benford formula.

• Zstat Ratio – Displays the Z-Stat ratio for each digit combination. The Z-statistic measures how far a particular result is from the expected value and is expressed in standard deviations. For example, a Z-statistic of 0.500 represents one-half of a standard deviation.

• Lower Bound (optional) – Displays digit frequencies that are significantly less than the expected result.

• Upper Bound (optional) – Displays digit frequencies that are significantly greater than the expected result.

Note

The Lower Bound and Upper Bound details are included only if the Include Upper and Lower Bounds checkbox is selected in the Benford dialog box and Zstat Ratio is not included in graph output.