The first significant digit in any number must be 1, 2, 3, 4, 5, 6, 7, 8, or 9. It was discovered t

Discussion in 'Calculator Requests' started by math_celebrity, Jan 8, 2017.

  1. math_celebrity

    math_celebrity Administrator Staff Member

    The first significant digit in any number must be 1, 2, 3, 4, 5, 6, 7, 8, or 9. It was discovered that first digits do not occur with equal frequency. Probabilities of occurrence to the first digit in a number are shown in the accompanying table. The probability distribution is now known as Benford's Law. For example, the following distribution represents the first digits in 231 allegedly fraudulent checks written to a bogus company by an employee attempting to embezzle funds from his employer.

    Digit, Probability
    1, 0.301
    2, 0.176
    3, 0.125
    4, 0.097
    5, 0.079
    6, 0.067
    7, 0.058
    8, 0.051
    9, 0.046

    Fradulent Checks
    Digit, Frequency
    1, 36
    2, 32
    3, 45
    4, 20
    5, 24
    6, 36
    7, 15
    8, 16
    9, 7

    Complete parts (a) and (b).

    (a) Using the level of significance &alpha; = 0.05, test whether the first digits in the allegedly fraudulent checks obey Benford's Law. Do the first digits obey the Benford's Law?<br />
    Yes or No

    Based on the results of part (a), could one think that the employe is guilty of embezzlement?
    Yes or No

    Show frequency percentages
    Digit Fraud Probability Benford Probability

    1 0.156 0.301

    2 0.139 0.176

    3 0.195 0.125

    4 0.087 0.097

    5 0.104 0.079

    6 0.156 0.067

    7 0.065 0.058

    8 0.069 0.051

    9 0.03 0.046

    Take the difference between the 2 values, divide it by the Benford's Value. Sum up the squares to get the Test Stat of 2.725281277
    Critical Value Excel: =CHIINV(0.95,8) = 2.733

    Since test stat is less than critical value, we cannot reject, so YES, it does obey Benford's Law and NO, there is not enough evidence to suggest the employee is guilty of embezzlement.
     

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