elinaikäkäyrät

Elinaikäkäyrät, also known as survival curves or failure time curves, are graphical representations used in various fields, particularly in medicine, engineering, and statistics, to illustrate the probability of an event occurring over time. The horizontal axis typically represents time, while the vertical axis shows the proportion of subjects or items that have not yet experienced the event of interest (e.g., death, failure, recovery) at a given time point.

These curves are often generated using methods like the Kaplan-Meier estimator, which is a non-parametric statistic used to estimate the survival function from lifetime data. The curve starts at 100% and decreases as more events occur. A sharp decline indicates a high rate of events, while a flatter curve suggests a slower rate.

In medical research, elinaikäkäyrät are commonly used to compare the effectiveness of different treatments. For instance, one curve might represent a control group, and another might represent a group receiving a new drug. If the drug-treated group's curve remains higher for longer, it suggests the drug is associated with improved survival or reduced event rates.

In engineering and reliability studies, these curves depict the probability of a component or system functioning without failure over time. They help in predicting the lifespan of products and in making informed decisions about maintenance and replacement. Statistical analysis is often performed alongside these curves to determine if observed differences between groups are statistically significant.