These are samples from a worksheet on Probability:
P(A and 1) P(a vowel and a number) P(heads and a 1 or 3)
These are all stand-alone phrases, not parts of equations. From numerous NBA workshop materials, I have deduced that the P for probability does not require the ELS in any of these examples. I think, from the explanation below, I understand why , but it seems anything but intuitive and so it would help to know what rule from the Nemeth Code would lead me to the same deduction -- the next time I encounter probability! Are there instances when the P followed by parentheses would require an ELS?
From NBA Professional Development Conference materials (Fall 2008) High School p61: partial example: P(A and B) comment: "P(A" are not single letters. If the opening grouping symbol and the space it occupies were removed, "P" and "A" would be adjacent and neither would require the ELI.
From NBA Abbreviations workshop materials (Spring 1999) p8: example: P(four or more breakdowns per day) = .1 comments: "P(four" -- if the opening grouping symbol and the space it occupies were removed, the letter would be followed by a word and not qualify as a single letter. All contractions are used within the grouping symbols as none are in contact with any symbols which forbid their use.
Rule IV sec 28a. says when only one letter or any combination of unspaced letters is in direct contact with only its opening or closing grouping sign, the ELI is used or not used as though the grouping signs were not present. P(A and B) the P is adjacent to the grouping sign which is followed by a letter. If you take out the grouping sign the P is in contact with the A -- so that A is no longer a single letter requiring a letter indicator. The B does need the ELI because if the grouping sign is removed, it is a single letter standing alone.
Rule IV sec 25a(vi) defines a single letter (in part) as followed by a space or a punctuation mark in print. A grouping sign is not a mark of punctuation. The P does not need the ELI in any of your examples because it does not meet the criteria for a single letter. Because it is not a single letter, it does not need the ELI.