This type of analysis reveals what actions should be taken. This is the most valuable kind of analysis and usually results in rules and recommendations for descriptive data analysis steps.
An analysis of likely scenarios of what might happen. The deliverables are usually a predictive forecast. A look at past performance to determine what happened and why. The result of the analysis is often an analytic dashboard. What is happening now based on incoming data. Prescriptive analytics is really valuable, but largely not used.
Where big data analytics in general sheds light on a subject, prescriptive analytics gives you a laser-like focus to answer specific questions. LDL cholesterol levels to determine where to focus treatment. Predictive analytics use big data to identify past patterns to predict the future. For example, some companies are using predictive analytics for sales lead scoring. Some companies have gone one step further use predictive analytics for the entire sales process, analyzing lead source, number of communications, types of communications, social media, documents, CRM data, etc. Diagnostic analytics are used for discovery or to determine why something happened.