In "a marginal improvement in scores", marginal means:
Marginal means slight or minor. In academic writing it usually signals the writer thinks the change was not important.
PTE Academic practice test
Questions 9 and 10 of 10
Which is correct? "The data ______ that the trend is slowing."
In academic and test English, data is treated as plural (the singular is datum), so it takes "suggest". Everyday speech often uses "suggests", but PTE marks the formal form.