The phrase "a different assumption" is correct and usable in written English.
You can use it when discussing an alternative belief or hypothesis that differs from a previously stated assumption.
Example: "In this study, we will explore a different assumption regarding the impact of climate change on agriculture."
Alternatives: "an alternative assumption" or "a contrasting assumption".
For if there was a logically consistent geometry differing from Euclid's only because it made a different assumption about the behaviour of parallel lines, it too could apply to physical space, and so the truth of (Euclidean) geometry could no longer be assured a priori, as Immanuel Kant had thought.
The difference is not unexpected, since complete cases analysis makes a different assumption from MI analysis.
Two perturbative solutions are developed, each based on a different assumption about the order of magnitude of the static displacements, produced by steady state wind forces.
Under a different assumption — that corporate taxes are mostly paid by workers because of the impact of the tax on investment, jobs and wages — the progressivity would be steeper.
The American approach to Pakistan was motivated by a different assumption: that Pakistani generals were operating under the illusion that if they stirred up enough trouble in Kashmir, the United States, fearing a conflict that could turn nuclear, would step in and insist that India make concessions.
We purposely chose very conservative assumptions and performed sensitivity analyses to test whether the results would qualitatively change if a different assumption were used". The authors conclude: "Access to appropriate public health practice is often determined by a small number of political leaders.
Each is formulated on a different premise with different underlying assumptions.
The Chinese start with a very different assumption: History is to be respected; if in doubt, follow the past rather than depart from it.
The fiction of the former Communist Europe was based on a very different assumption, one that seems naïve and old-fashioned in its collective optimism to readers in the disillusioned democracies.
Because these life-cycle studies involved a number of different assumptions, a range of results was reported, rather than a single value.
