The phrase "make a speculation" is correct and usable in written English.
You can use it when you want to suggest something that is likely to be true but cannot be proved. For example, "Let's make a speculation about what caused the market crash last week."
Analysts and investors have wondered for weeks whether Nestlé was preparing to make a bid, speculation that grew on Monday after Nestlé, based in Switzerland, said it would sell its remaining stake in the eye care company Alcon for $28.1 billion.
Although there has been no indication from the White House on when Mr. Bush might make a decision, speculation in Washington has recently focused on a possible announcement during January's State of the Union address.
"When you see one of the fastest growing corporations in a cash shortage, you have to ask: Where did that cash go?" With a definitive answer to this question a long way off, Mr. McCullough is willing to make an informed speculation about why Enron unraveled as it did.
Aviation experts say it is far too early to make an informed speculation about what could have caused the crash, because an extensive list of possible human and mechanical problems could explain the accident.
Even inefficient, poorly designed plants could make a profit, and speculation in solar building permits was common.
Would her symptoms (those that still exist) diminish if she could be given a rest from investigation and allowed a more normal and happy childhood?" Ned Jackson makes a darker speculation in the affidavit.
"The state is asking you to make a judgment based on speculation and conjecture," defense attorney Joseph Murtha told jurors in his closing argument.
In Britain, traders buying and selling bitcoin no longer have to pay VAT on their purchases of the currency, but are instead liable for capital gains tax or income tax if they make a profit on their speculation.
However, Gawker refused to take their article down as they were simply reporting what another outlet published and instead offered him a chance to make a comment about the speculation on its website.
In the section on "Possible mechanism of substitution of the critically-conserved R residue" the authors make a rather far-fetched speculation that Giardia might have once harbored two orthologous Sec61alpha genes allowing for the functional substitution in one of them with a concomitant mutation in the rRNA.
