Calculating 5 different ranges for people resource management I am working on a project for my company. My team is building a project charter template. In this template needs to be a drop down that estimates how many full-time employee days(FTE) will be estimated to be used for each project someone will be working on in the future. 
I have all the data from the previous year and the goal is to have $4-5$ different ranges in this drop down based off of previous years data. So for example, the drop down would have $2-5$ FTE, $6-9$ FTE, $10-15$ FTE, $15-25$ FTE, $26+$ FTE. The issue is leadership wants this based off past data.
How do I analyze the data and have an output that reflects specific ranges? Originally, the idea was just a low, medium, high, but now leadership wants $4-5 $ ranges and data to back it up with. 
 A: If you just want to justify the choice of ranges, you can look at past projects and make each range a quintile of the distribution.  You could also plot a histogram of the number of FTEs per project.  Maybe (but don't hold your breath) you will have natural gaps in your distribution, like you do lots of $2-6$ FTE projects but very few $7-10$ ones.  It makes sense to put the breaks between your ranges in the dips.  Both of these approaches meet the request of being based on past data.  
You don't talk about it, but the useful thing is probably to guess which range a given proposed project fits into.  Say you are a full service homebuilding/remodeling contractor.  One project might be to convince a prospective client to hire you. That could take a couple day's of sketching, meetings to show the results, and answering a few questions.  Once hired, you might spend 15 FTEs making full plans for approval.  You also offer the service to do the construction work, which will take much more.  You could look at past projects to try to make a model of what kind of project takes how much work.
