Lean Principles and Waste
Lean is a way of thinking about work as a flow that delivers value to a customer while removing everything that does not. Start with the five core principles: specify value from the customer's perspective, map the value stream, create flow, let the customer pull, and pursue perfection. Value is defined only by the customer; anything that consumes resources without adding value from that viewpoint is waste. Candidates must be able to distinguish value-adding activity (changes the product or service in a way the customer pays for, done right the first time) from necessary non-value-adding activity (e.g. regulatory inspection, legal paperwork), which Lean seeks to reduce but cannot always eliminate.
The eight wastes are commonly remembered by the mnemonic TIMWOODS: Transport, Inventory, Motion, Waiting, Overproduction, Overprocessing, Defects, and Skills (unused talent). Overproduction is traditionally called the worst waste because it hides and creates the others. Be careful: inventory waste refers to excess stock, not the existence of any buffer; motion waste applies to people, transport waste applies to materials and information.
Trap to watch: questions often present a scenario and ask which waste it is. Read who or what is moving. A clerk walking to a printer is motion; documents being routed between departments is transport. Also distinguish value stream mapping (current and future state) from a simple process map.
Rule of thumb: before labelling a waste, ask 'would the customer pay for this step?' If no, and it can be removed without harm, it is waste to eliminate. If it is required by law or safety, it is necessary non-value-adding and should be minimised, not simply cut.