The phrase "a second assumption is that" is correct and usable in written English.
It can be used when introducing an additional assumption in a discussion or argument, particularly in academic or analytical writing.
Example: "In our analysis of the data, a second assumption is that the variables are independent of each other."
Alternatives: "Another assumption is that" or "A further assumption is that".
A second assumption is that the financial sector will accept the new arrangements in perpetuity.
A second assumption is that all effects that match the global signal are of no interest and can be removed.
A second assumption is that it is safe to cut alfalfa if there are less than 200 GDD (base5 C) remaining before the first killing frost, as there would be insufficient regrowth to use up enough storage carbohydrates to negatively affect alfalfa persistence.
A second assumption is that single sets of selected areas are adequate indicators of incidental representation or the species accumulation index.
A second assumption is that clustering applied to the expression data will identify co-regulated groups of genes, or, alternately, that it captures important trends in the data that may arise from multiple influences.
A second assumption is that a link exists between P4P indicators and true improvements in quality.
A second assumption was that as the caliphate lost territory in the Middle East, the ISIS brand would gradually lose credibility.
A second assumption was that the right and left limbs were comparable on the outset (i.e., no dominant side).
A second assumption was that the costs of mental workload would show up as greater variability in item responses for older adults within each of the five constructs, which might result in reduced likelihood of identifying the expected five factors in a very brief Big Five inventory.
A fourth assumption is that human nature is intensely social.
A first assumption is that the planet should have moderate seasons.
