Overhead refers to equipment or costs for a business or major project that are not related to any specific task, but are still necessary for the business or project to function. For a business, the accounting department is considered overhead. If I am an engineer, I do not need the accounting department to finish my individual work, but I need them overall to pay my expenses and paycheck, as well as collecting money from customers. Also, pencils, computers, printers - used in general - would be considered as overhead. I cannot say their cost is applied to any one job that I do, but I still need them (the pencils less these days). In the example you give above, the overhead is the effort needed to perform the analyses - gathering the data, organizing it.