Analyse d'association: concepts et algorithmes de base (document en anglais)

1. For each of the following questions, provide an example of an association rule

from the market basket domain that satisfies the following conditions. Also,

describe whether such rules are subjectively interesting.

(a) A rule that has high support and high confidence.

Answer: Milk −→ Bread. Such obvious rule tends to be uninteresting.

(b) A rule that has reasonably high support but low confidence.

Answer: Milk −→ Tuna. While the sale of tuna and milk may be

higher than the support threshold, not all transactions that contain milk

also contain tuna. Such low-confidence rule tends to be uninteresting.

(c) A rule that has low support and low confidence.

Answer: Cooking oil −→ Laundry detergent. Such low confidence rule

tends to be uninteresting.

(d) A rule that has low support and high confidence.

Answer: Vodka −→ Caviar. Such rule tends to be interesting.

2. Consider the data set shown in Table 6.1.

(a) Compute the support for itemsets {e}, {b, d},and {b, d, e} by treating

each transaction ID as a mTable 6.1. Example of market basket transactions.

Customer ID Transaction ID Items Bought

1 0001 {a, d, e}

1 0024 {a, b, c, e}

2 0012 {a, b, d, e}

2 0031 {a, c, d, e}

3 0015 {b, c, e}

3 0022 {b, d, e}

4 0029 {c, d}

4 0040 {a, b, c}

5 0033 {a, d, e}

5 0038 {a, b, e}

s({e})= 8

10

=0.8

s({b, d})= 2

10

=0.2

s({b, d, e})= 2

10

=0.2

(6.1)

(b) Use the results in part (a) to compute the confidence for the association

rules {b, d}−→{e} and {e}−→{b, d}. Is confidence a symmetric

measure?

Answer:

c(bd −→ e)= 0.2

0.2

= 100%

c(e −→ bd)= 0.2

0.8

= 25%

No, confidence is not a symmetric measure.

(c) Repeat part

...