"rash speculation" is correct and usable in written English.
You can use it when you want to describe someone who is making a guess about something without taking the time to consider facts or evidence. For example: "His rash speculation that he'd win the lottery didn't come to pass."
But that is rash speculation, at this point.
"Seeking to lay the blame for the enormous Internet bubble solely at the feet of Merrill Lynch, plaintiffs would have this court conclude that the federal securities laws were meant to underwrite, subsidize and encourage their rash speculation in joining a freewheeling casino that lured thousands obsessed with the fantasy of Olympian riches".
In the past, for example, risk assessment has been lampooned as a series of unsubstantiated assumptions compounded by rash speculation.
Opinions differ as to the cause of his collapse: on his own admission, Defoe was apt to indulge in rash speculations and projects; he may not always have been completely scrupulous, and he later characterized himself as one of those tradesmen who had "done things which their own principles condemned, which they are not ashamed to blush for".
The latest rash of speculation about Cook and the captaincy was provoked by a nightmarish day for the England captain in Pallekele.
Lt Gen Ali Mamlouk, the head of the country's national security council, was reported on Monday to be under house arrest in the Syrian capital following a rash of speculation about his whereabouts at a time of deepening crisis for the regime.
Most of the current rash of speculation centers on claims that top political operatives in the Clinton camp have launched the transparent and clumsy gambit of "strategic leaks" designed to "box" in the President-elect and compel him to appoint his former rival for the Democratic presidential nomination.
On an Internet forum about so-called airplane chemtrails, "Anonymous" from Portland, Ore., said he'd heard speculation that the rashes might be psychosomatic and resented it enormously.
That has led to a series of product recalls, a rash of bad public relations and widespread speculation that Aventis would divest itself of the agriculture unit.
Coughlin — faced with a rash of injuries, distractions like the talk of Tiki Barber's retirement and the endless speculation over his job status — considered it one of his better coaching jobs.
