As likely as not and For certain

For certain and as likely as not are semantically related. In some cases you can use "For certain" instead an adverb phrase "As likely as not".

For certain adverb - Definitely or positively (`sure' is sometimes used informally for `surely').

As likely as not and for certain are semantically related. Sometimes you can use "As likely as not" instead an adverb phrase "For certain".