The phrase "also speculated that a" is correct and usable in written English.
It can be used when discussing theories or hypotheses regarding a particular subject or event.
Example: "The researchers also speculated that a significant correlation exists between the two variables."
Alternatives: "also suggested that a" or "also theorized that a".
Ms. Herzog also speculated that a new company could achieve significant savings by combining the two sales forces.
Some market watchers have also speculated that a fat finger trade, where someone accidentally omits a decimal point or types the wrong number, could have been a factor.
Last month, researchers at Symantec also speculated that a string of numbers found in the program — 19790509 — while seeming random, might actually be significant.
Mr. Cha, who served on the staff of the National Security Council during the Bush administration, also speculated that a visit by the men might encourage Kim Jong-un, the young North Korean leader, to relax the state's rigid controls on information.
At his monthly press conference, Block also speculated that a rash of armored car robberies in the Southland--12 in the last year--may be the work of a single gang.
These authors also speculated that a decrease in satisfaction with social contacts may result in urban contexts, lowering life satisfaction for Turkish elderly.
She also speculated that an increase in the amount of junk mail may have made people hostile to unsolicited mail.
Muula and Phiri 72 also speculated that an increase in poverty during the 1990s could have contributed to an increase in MMR.
He also speculates that time may help, as a generation more comfortable with sex toys ages and starts to develop mobility issues and demand more of producers en masse.
One may also speculate that frail older patients may have a reduced compensatory capacity for the physiological alterations that may occur upon drug treatment changes.
We also speculate that a simple, more standardized technique might help improve monitoring of IAP.
