The correct answer is: C. both minimum support and confidence are needed.
To determine association rules from frequent item sets, both minimum support and confidence are needed. Minimum support is the minimum percentage of transactions in the dataset that must contain an item set in order for it to be considered frequent. Minimum confidence is the minimum percentage of transactions that contain an item set A also contain item set B, in order for the rule A â B to be considered valid.
For example, if the minimum support is 0.1 and the minimum confidence is 0.5, then the rule “A â B” would be considered valid if 10% of the transactions in the dataset contain both A and B, and if 50% of the transactions that contain A also contain B.
Here is a more detailed explanation of each option:
- Option A: only minimum confidence needed. This is incorrect because minimum support is also needed. For example, if the minimum support is 0.1 and the minimum confidence is 0.5, then the rule “A â B” would not be considered valid if only 5% of the transactions in the dataset contain both A and B, even if 50% of the transactions that contain A also contain B.
- Option B: neither support not confidence needed. This is incorrect because both minimum support and confidence are needed.
- Option C: both minimum support and confidence are needed. This is the correct answer.
- Option D: minimum support is needed. This is incorrect because minimum confidence is also needed.