Cybersecurity The accompanying Statdisk results shown in the margin are obtained from the data given in Exercise 1. What should be concluded when testing the claim that the leading digits have a distribution that fits well with Benford’s law?

Short Answer

Expert verified

There is enough evidence to warrant rejection of the claim that the leading digits have a distribution that fits well with Benford’s law.

Step by step solution

01

Given information

The observed frequencies and the expected frequencies of the leading digits of inter-arrival traffic times are tabulated.

02

Hypothesis testing

The following hypotheses are set up to test for the goodness of fit test of the given distribution:

Null Hypothesis:

The null hypothesis is that in which the proportions of all the leading digits should be equal to the claimed value. In other words, thedistribution of the leading digits fits well with Benford’s law.

Alternative Hypothesis:

The alternative hypothesis is that in which thedistribution of the leading digits does not fit well with Benford’s law.

The test statistic value\(\left( {{\chi ^2}} \right)\)is equal to 20.9222.

The corresponding p-value is equal to 0.0074.

The critical chi-square value is 15.5073.

Assume the significance level is 0.05.

Since the test statistic is greater than the critical value, so the null hypothesis is rejected.

Since the p-value is less than 0.05, the null hypothesis is rejected.

Thus, there is enough evidence to warrant rejection of the claim that the leading digits have a distribution that fits well with Benford’s law.

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Most popular questions from this chapter

A study of people who refused to answer survey questions provided the randomly selected sample data shown in the table below (based on data from “I Hear You Knocking But You Can’t Come In,” by Fitzgerald and Fuller, Sociological Methods and Research,Vol. 11, No. 1). At the 0.01 significance level, test the claim that the cooperation of

the subject (response or refusal) is independent of the age category. Does any particular age group appear to be particularly uncooperative?

Age


18-21

22-29

30-39

40-49

50-59

60 and over

Responded

73

255

245

136

138

202

Refused

11

20

33

16

27

49

In Exercises 5–20, conduct the hypothesis test and provide the test statistic and the P-value and , or critical value, and state the conclusion.

California Daily 4 Lottery The author recorded all digits selected in California’s Daily 4 Lottery for the 60 days preceding the time that this exercise was created. The frequencies of the digits from 0 through 9 are 21, 30, 31, 33, 19, 23, 21, 16, 24, and 22. Use a 0.05 significance level to test the claim of lottery officials that the digits are selected in a way that they are equally likely.

In a study of the “denomination effect,” 43 college students

were each given one dollar in the form of four quarters, while 46 other college students were each given one dollar in the form of a dollar bill. All of the students were then given two choices: (1) keep the money; (2) spend the money on gum. The results are given in the accompanying table (based on “The Denomination Effect,” by PriyaRaghubir and Joydeep Srivastava, Journal of Consumer Research,Vol. 36.) Use a 0.05 significance level to test the claim that whether students purchased gum or kept the money is independent of whether they were given four quarters or a \(1 bill. Is there a “denomination effect”?

Purchased Gum

Kept the Money

Students Given Four Quarters

27

16

Students Given a \)1 Bill

12

34

Loaded Die The author drilled a hole in a die and filled it with a lead weight, then proceeded to roll it 200 times. Here are the observed frequencies for the outcomes of 1, 2, 3, 4, 5, and 6, respectively: 27, 31, 42, 40, 28, and 32. Use a 0.05 significance level to test the claim that the outcomes are not equally likely. Does it appear that the loaded die behaves differently than a fair die?

Cybersecurity What do the results from the preceding exercises suggest about the possibility that the computer has been hacked? Is there any corrective action that should be taken?

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