keskisaika

Keskisaika is a Finnish term meaning mean time or average time. In statistics and operations research, it refers to the expected duration of a process or event, expressed as the average of observed times or as the theoretical mean of a probability distribution. Etymologically, keski- means center and aika means time.

Calculation and concept: The basic definition is the arithmetic mean of observed durations: (t1 + t2 + ... + tn) / n. In probabilistic terms, keskisaika equals the expected value of the random duration T, E[T], when the distribution is known. For distributions common in reliability or queuing theory, the theoretical keskisaika is the distribution’s mean (for example, the exponential distribution has mean 1/λ).

Contexts and examples: It is used across fields to summarize how long tasks, processes, or system responses take. Examples include the average processing time of a manufacturing step, the average response time of a web service, or the mean time to resolve a customer support ticket.

Considerations: The keskisaika can be distorted by outliers or skewed data; in such cases the median or a trimmed mean may provide a more robust summary. When reporting, it is common to accompany the value with a measure of variability, such as standard deviation or a confidence interval.

See also: arithmetic mean, expected value, median, MTBF, MTTR, service level.