Blackball (pool) number "8" (a holdover from kelly pool), though numberless variants are not unknown. British pool tables come in 6 × 3 foot (1.8 × 0.9 m) or 7 × 3.5 ft (2.12 × 1.06 m) varieties, with 7 feet being the regulation size for league play. The table has pockets just larger than the balls and rounded, as in the game of snooker, whereas the international-style (or "American-style") table has pockets significantly wider, with pointed . Tournament rules may require the presence of more than one type of (mechanical bridge), as in snooker. There are two competing standards bodies that
Standard normal table probability that a statistic is between 0 (the mean) and Z. Note that for z = 1, 2, 3, one obtains (after multiplying by 2 to account for the [-z,z] interval) the results f(z) = 0.6827, 0.9545, 0.9974, characteristic of the 68–95–99.7 rule. This table gives a probability that a statistic is less than Z (i.e. between negative infinity and Z). The values are calculated using the cumulative distribution function of a standard normal distribution with mean of zero and standard deviation of one, usually denoted with the capital Greek letter formula_4 (phi), is the integral formula_4(z) is related to