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Each standard deviation represents a fixed percentile. Thus, rounding to two decimal places, −3σ is the 0.13th percentile, −2σ the 2.28th percentile, −1σ the 15.87th percentile, 0σ the 50th percentile (both the mean and median of the distribution), +1σ the 84.13th percentile, +2σ the 97.72nd percentile, and +3σ the 99
In mathematics, a percentage (from Latin per centum 'by a hundred') is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign (%), [ 1] although the abbreviations pct., pct, and sometimes pc are also used. [ 2] A percentage is a dimensionless number (pure number), primarily used for expressing proportions ...
In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.
Suppose East is known to have 7 spades from the bidding and after seeing dummy you deduce West to hold 2 spades; then if your two lines of play are to hope either for diamonds 5-3 or clubs 4-2, the a priori probabilities are 47% and 48% respectively but and so now the club line is significantly better than the diamond line.
The table shows what number the order of magnitude aim at for base 10 and for base 1 000 000. It can be seen that the order of magnitude is included in the number name in this example, because bi- means 2, tri- means 3, etc. (these make sense in the long scale only), and the suffix -illion tells that the base is 1 000 000 .
Isotopes of silicon (14Si) Silicon ( 14 Si) has 23 known isotopes, with mass numbers ranging from 22 to 44. 28 Si (the most abundant isotope, at 92.23%), 29 Si (4.67%), and 30 Si (3.1%) are stable. The longest-lived radioisotope is 32 Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately ...
Thallium ( 81 Tl) has 41 isotopes with atomic masses that range from 176 to 216. 203 Tl and 205 Tl are the only stable isotopes and 204 Tl is the most stable radioisotope with a half-life of 3.78 years. 207 Tl, with a half-life of 4.77 minutes, has the longest half-life of naturally occurring Tl radioisotopes.
B. , the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 to 21, all with short half-lives, the longest being that of 8. B. , with a half-life of only 771.9 (9) ms and 12. B. with a half-life of 20.20 (2) ms. All other isotopes have half-lives shorter than 17.35 ms.