6. Define a change in estimate and provide an illustration. When is a change in accounting estimate effected by a change in accounting principle?

For this question, emphasis is on need for example. Please provide a unique example about change in estimate. Thank you

A change in an estimate is simply a change in the way an individual perceives the realizability of an asset or liability. Examples of changes in estimate are: (1) change in the realizability of trade receivables, (2) revisions of estimated lives, (3) changes in estimates of warranty costs, and (4) change in estimate of deferred charges or credits. A change in accounting estimate affected by a change in accounting principle occurs when a change in accounting estimate is inseparable from the effect of a related change in accounting principle. An example would be switching from capitalizing advertising expenditures to expensing them if the future benefit of the expenditures can no longer be estimated with reasonable certainty.