Observation is a method of data collection that involves physically observing how a system operates and how it is used. Observations are typically performed when designing a system that will replace a current system, and are useful when attempting to solve a problem with an existing system. For example, a system may become particularly slow at certain times of the day, but will work well outside of those times. An observation of users at the time when the system slows would be useful in helping determine why the issue has occurred. Similarly, systems may have wildly varying performance depending on the time of year, such as consumer websites during periods of high sales such as Boxing Day or the end of the financial year (EOFY). Observations can also be used when creating a new system that will replace something that is currently being completed manually. In these instances, the manual process is observed and documented. Advantages of observations are that they can provide an unbiased view of the system; information can be gathered without asking for a user's opinion or relying on their memory. Observations can also occur simultaneously as long as users are located in the same physical space. Disadvantages are that they are quite time-consuming and therefore very expensive if they need to occur more than once or over a long period of time. Time-specific observations can also be very difficult if the project timeline does not allow for it; for example, waiting for the end of the financial year may require waiting 12 months. Similarly, if the observations occur at the wrong time, the results may not be very useful as they may not be representative of how the system is typically used. Another disadvantage is that people can become very self-conscious when they are being observed, so their actions may not necessarily be the same as if they were alone, resulting in inaccurate data.