What is the requirement for submitting a revised workshop paper to a conf in CS?

We have published a workshop paper last year. Now, we are planning to submit it to a conference. The conference paper roughly have 50% new materials. Basically, the workshop paper studied a 3.5-year data set while the conf version extends it to 4.5-year. The conf version also has a new data set. We also applied several new analysis methods to the data, obtaining new results.

My question is, is 50% new material enough for a new conference publication? Also, can I reuse the analysis methods in the workshop paper? What about reusing some text?

Thank you very much!