Consider the data set shown in Table 7.12.

Question

(a) For each combination of rules given below, specify the rule that has the

highest confidence.

i. 15
and 15
ii. 15
15
iii. 15
(b) Suppose we are interested in finding the average number of hours spent

online per week by Internet users between the age of 15 and 35. Write

the corresponding statistics-based association rule to characterize the

segment of users. To compute the average number of hours spent online,

approximate each interval by its midpoint value (e.g., use B = 7.5 to

represent the interval 5
Test whether the quantitative association rule given in part (b) is sta-

tistically significant by comparing its mean against the average number

of hours spent online by other users who do not belong to the age group.

Answer 1

(a)

I. Both 15
10
ii. The rule 15
(83.3%).

iii. The rule 10
(73.8%).

(b) There are 65 people whose average age is between 15 and 35.

The average number of hours spent online is

2.5×12/65 + 7.5×20/65 + 15×15/65 + 25×13/65 + 35×5/65 = 13.92.

Therefore the statistics-based association rule is:

15 ? A < 35 ?? B : ? = 13.82.

(c) 2.5 × 6/35 + 7.5 × 9/35 + 15 × 10/35 + 25 × 6/65 + 35 × 4/65 = 14.93.

The standard deviations for the two groups are 9.786 (15 ? Age < 35)

and 10.203 (Age < 15 or Age ? 35), respectively.





The difference is not significant at 95% confidence level.