Question

An investigator analyzed the leading digits from 787 checks issued by seven suspect companies. The frequencies were found to be 4​, 11​, 2​, 72​, 371​, 281​, 7​, 16​, and 23​, and those digits correspond to the leading digits of​ 1, 2,​ 3, 4,​ 5, 6,​ 7, 8, and​ 9, respectively. If the observed frequencies are substantially different from the frequencies expected with​ Benford's law shown​ below, the check amounts appear to result from fraud. Use a 0.025 significance level to test for​ goodness-of-fit with​ Benford's law. Does it appear that the checks are the result of​ fraud?

Leading Digit:      1    2    3 4 5 6    7 8 9
Actual Frequency:      4 11    2    72    371 281 7    16    23

Benford's Law:      30.1% 17.6% 12.5%    9.7%    7.9% ​ 6.7%    ​5.8% ​ 5.1%    ​4.6%

Determine the null and alternative hypotheses.

Ho​: (1)_________________    H1​: (2)_________________

Calculate the test​ statistic, χ2.

χ2 = _______________​

(Round to three decimal places as​ needed.)

Calculate the​ P-value.

P-value = _______________​

(Round to four decimal places as​ needed.)

State the conclusion.

(3)_________________Ho. There (4)______________sufficient evidence to warrant rejection of the claim that the leading digits are from a population with a distribution that conforms to​ Benford's law. It (5)________________that the checks are the result of fraud.

Choose from the following options:
(1) a. At least two leading digits have frequencies that do not conform to Benford's    law.
b. The leading digits are from a population that conforms to Benford's law.
c. At most three leading digits have frequencies that do not conform to Benford's law.
d. At least one leading digit has a frequency that does not conform to Benford's law.

(2) a. The leading digits are from a population that conforms to Benford's law.
b. At most three leading digits have frequencies that do not conform to Benford's    law.
c. At least one leading digit has a frequency that does not conform to Benford's    law.
   d. At least two leading digits have frequencies that do not conform to Benford's law.

(3) Do not reject
   Reject

(4) is
   is not

(5) does appear
   does not appear

Answer 1

Ho​: The leading digits are from a population that conforms to Benford's law.

Ha: At least one leading digit has a frequency that does not conform to Benford's    law.

applying chi square goodness of fit test:

	relative	observed	Expected		Chi square
Category	frequency(p)	Oi	Ei=total*p		R2i=(Oi-Ei)2/Ei
1	0.3010	4	236.89		228.95
2	0.1760	11	138.51		117.39
3	0.1250	2	98.38		94.42
4	0.0970	72	76.34		0.25
5	0.0790	371	62.17		1534.01
6	0.0670	281	52.73		988.22
7	0.0580	7	45.65		32.72
8	0.0510	16	40.14		14.52
9	0.0460	23	36.20		4.81
total	1.00	787	787		3015.28
test statistic X2=		3015.279

p value =

0.0000

from excel: chidist(3015.279,8)

reject Ho , there is sufficient evidence to warrant rejection of the claim that the leading digits are from a population with a distribution that conforms to​ Benford's law. It does appear that the checks are the result of fraud.