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The asteroid Toutatis is listed as a potentially hazardous near-Earth asteroid, yet poses no immediate threat to Earth.(Radar image taken by GDSCC in 1996.)A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of ...
The table shown on the right can be used in a two-sample t-test to estimate the sample sizes of an experimental group and a control group that are of equal size, that is, the total number of individuals in the trial is twice that of the number given, and the desired significance level is 0.05. [4]
The theoretical return period between occurrences is the inverse of the average frequency of occurrence. For example, a 10-year flood has a 1/10 = 0.1 or 10% chance of being exceeded in any one year and a 50-year flood has a 0.02 or 2% chance of being exceeded in any one year.
Background radiation originates from a variety of sources, both natural and artificial. These include both cosmic radiation and environmental radioactivity from naturally occurring radioactive materials (such as radon and radium ), as well as man-made medical X-rays, fallout from nuclear weapons testing and nuclear accidents .
Initially, forecasters predicted tides up to 14 feet (4.3 m) above normal along the East Coast of Florida, near the potential location of landfall. [2] However, the National Hurricane Center later noted that storm surge up to 10 feet (3.0 m) would occur along the East Coast of Florida, as high as 13 feet (4.0 m) in Biscayne Bay, and a height of 11 feet (3.4 m) of the West Coast of Florida.
Peak ground acceleration can be expressed in fractions of g (the standard acceleration due to Earth's gravity, equivalent to g-force) as either a decimal or percentage; in m/s 2 (1 g = 9.81 m/s 2); [7] or in multiples of Gal, where 1 Gal is equal to 0.01 m/s 2 (1 g = 981 Gal).
Although p-values are helpful in assessing how incompatible the data are with a specified statistical model, contextual factors must also be considered, such as "the design of a study, the quality of the measurements, the external evidence for the phenomenon under study, and the validity of assumptions that underlie the data analysis". [3]
Statistical significance dates to the 18th century, in the work of John Arbuthnot and Pierre-Simon Laplace, who computed the p-value for the human sex ratio at birth, assuming a null hypothesis of equal probability of male and female births; see p-value § History for details.