Billiard table ivory balls from warping. The first use of electric heating was for an 18.2 balkline tournament held in December 1927 between Welker Cochran and Jacob Schaefer, Jr. The New York Times announced it with fanfare: "For the first time in the history of world's championship balkline billiards a heated table will be used..." A pool table, or pocket billiards table, has six – one at each corner of the table () and one at the midpoint of each of the longer sides ( or ). Pool tables come in different sizes, typically referred to as , , , or tables.
Normally distributed and uncorrelated does not imply independent the difference "X" − "Y" is nowhere near being normally distributed, since it has a substantial probability (about 0.88) of it being equal to 0. By contrast, the normal distribution, being a continuous distribution, has no discrete part—that is, it does not concentrate more than zero probability at any single point. Consequently "X" and "Y" are not "jointly" normally distributed, even though they are separately normally distributed. Normally distributed and uncorrelated does not imply independent In probability theory, although simple examples illustrate that linear uncorrelatedness of two random variables does not in general imply their independence, it is sometimes mistakenly