When would you use GROUP BY ROLLUP clause in your OLAP query?

What is an appropriate data visualization to use in a presentation for an analyst audience?

Under which circumstance do you need to implement N-fold cross-validation after creating a regression model?

Consider a database with 4 transactions:
Transaction 1: {cheese, bread, milk}
Transaction 2: {soda, bread, milk}
Transaction 3: {cheese, bread}
Transaction 4: {cheese, soda, juice}
The minimum support is 25%. Which rule has a confidence equal to 50%?

You are using the Apriori algorithm to determine the likelihood that a person who owns a home has a good credit score. You have determined that the confidence for the rules used in the algorithm is > 75%. You calculate lift = 1.011 for the rule, “People with good credit are homeowners”. What can you determine from the lift calculation?

Consider a database with 4 transactions:
Transaction 1: {cheese, bread, milk}
Transaction 2: {soda, bread, milk}
Transaction 3: {cheese, bread}
Transaction 4: {cheese, soda, juice}
You decide to run the association rules algorithm where minimum support is 50%. Which rule has a confidence at least 50%?

Which word or phrase completes the statement? Data-ink ratio is to data visualization as __________ .