Number Alive
Number Alive - Related Videos
02:56
C. elegans Survival Assay: A Short-Term Toxicity Test
0 Views •
2023
This video introduces a short-term survival assay that tests a treatment for acute toxicity or tests a genetic strain for resistance to a toxic condition. The example protocol shows an example survival assay in which worms are tested for their ability to resist oxidative stress induced by paraquat (PQ).
12:49
Measuring Caenorhabditis elegans Life Span on Solid Media
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Cited by 201 •
2009
In this article we present a general protocol for measuring life span of nematodes maintained on solid media with UV-killed bacterial food.
01:34
Groupthink
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2020
When in group settings, we are often influenced by the thoughts, feelings, and behaviors around us. Groupthink is another phenomenon of conformity where modification of the opinions of members in a group aligns with what they believe is the group consensus (Janis, 1972). In such situations, the group often takes action that individuals would not perform outside the group setting because groups make more extreme decisions than individuals do. Moreover, groupthink can hinder opposing trains of...
08:44
Invertebrate Lifespan Quantification
0 Views •
2023
Many animals naturally stop growing upon reaching adulthood, after which they undergo aging or "senescence" until dying. The amount of time between an organism\'s birth and death is called its lifespan, which can be influenced by various biological and environmental factors. By exposing organisms to different growth conditions, scientists can better understand the factors affecting lifespan. Flies and worms are ideal organisms to perform such experiments, given their short generation time and...
02:48
Radioactive Decay and Radiometric Dating
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2020
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time. The SI unit for activity is the becquerel, which is one disintegration per second. Another unit of activity is the...
FAQs
The count supplies the observed number of survivors at a particular age or time, while the survival function expresses survival across those time points. By arranging counts from follow-up data or a life table, researchers can examine how survival changes as time progresses. This makes Number alive a foundational input for describing mortality patterns rather than a complete survival estimate by itself.
Censoring identifies individuals whose observation ends before researchers record a death. Because these individuals cannot automatically be treated as deceased or as fully observed survivors, their status must remain distinct in the follow-up record. Separating deaths from censored observations helps life tables and survival models use the available information without confusing incomplete observation with mortality.
A Number alive value has meaning only in relation to the age or time point, the population being followed, and the observation process. Changing the cohort definition or comparing different time points can produce different counts even when the underlying mortality pattern is similar. Clear population and time specifications therefore support valid comparisons across studies or periods.
Researchers first define the study cohort and the time or age at which survival will be assessed. They then track each individual’s entry into observation, recorded death, or censoring during follow-up. At the selected point, the resulting records identify the observed survivors. The same information can subsequently support a life table or survival model.
The measure is useful when investigators need to compare survival or mortality patterns among treatments, populations, or time periods. In clinical research, it can summarize follow-up outcomes for a cohort. In epidemiology and demographic analysis, it helps describe population survival, while actuarial calculations use related information to evaluate survival patterns over time.
Counts organized across successive ages or time points provide a basis for broader survival summaries. Life tables can use those observations to derive survival-related estimates, including life expectancy, while actuarial analyses can examine how survival patterns differ across populations or periods. The value of the count lies in its role as an observable component of these statistical calculations.