How many drops of CSF is enough?

Sample size: how many is enough?

Sample size is an element of research design that significantly affects the validity and clinical relevance of the findings identified in research studies. Factors that influence sample size include the effect size, or difference expected between groups or time points, the homogeneity of the study participants, the risk of error that investigators consider acceptable and the rate of participant...

How many doctors are enough?

How Many Earths Are Enough?

The goals of NASA’s Terrestrial Planet Finder (TPF) and ESA’s Darwin missions are to find and characterize terrestrial planets in the habitable zones of other stars, and to search for evidence of life in the atmospheres of any planets found. A key issue that must be addressed is the size of the sample of stars that must be searched before the scientific community, the funding agencies, and the ...

How Many Is Enough?—Statistical Principles for Lexicostatistics

Lexicostatistics has been applied in linguistics to inform phylogenetic relations among languages. There are two important yet not well-studied parameters in this approach: the conventional size of vocabulary list to collect potentially true cognates and the minimum matching instances required to confirm a recurrent sound correspondence. Here, we derive two statistical principles from stochasti...

How many events is enough? Are you positive?

ONE of the more perplexing problems in flow cytometry revolves around the issue of: ‘‘Is it real’’? If a sample has one event in a particular gate, is that event real? Is it significant? Should it be believed? Is the sample ‘‘positive’’? If the answer to these is ‘‘No’’, then what is the threshold number of events above which the answer becomes ‘‘Yes’’? Flow cytometry is unique among biological...