# Answer consider the following pair of rules and their

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Answer: Consider the following pair of rules and their confidence levels : No. Rule Conf. 1. persons P , 10000 < P . salary 20000 P . credit = good 60% 2. persons P , 20000 < P . salary 30000 P . credit = good 90% The new rule has to be assigned a confidence-level which is between the confidence-levels for rules 1 and 2. Replacing the original rules by the new rule will result in a loss of confidence-level information for classifying persons, since we cannot distinguish the confidence levels of perople earning between 10000 and 20000 from those of people earning between 20000 and 30000. Therefore we can combine the two rules without loss of information only if their confidences are the same. 20.4 Consider the schema depicted in Figure 20.2. Give an SQL query to summarize sales numbers and price by store and date, along with the hierarchies on store and date. Answer: query: select store-id , city , state , country , date , month , quarter , year , sum ( number ), sum ( price ) from sales , store , date where sales.store-id = store.store-id and sales.date = date.date groupby rollup ( country , state , city , store-id) , rollup ( year , quarter , month , date ) 20.5 Consider a classification problem where the classifier predicts whether a person has a particular disease. Suppose that 95% of the people tested do not suffer from the disease. (That is, pos corresponds to 5% and neg to 95% of the test cases.) Consider the following classifiers:

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• Spring '13
• Dr.Khansari
• Data Mining, source-driven architecture

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