  Context: Requirements quality can have a substantial impact on the
effectiveness and efficiency of using requirements artifacts in a development
process. Quantifiers such as "at least", "all", or "exactly" are common
language constructs used to express requirements. Quantifiers can be formulated
by affirmative phrases ("At least") or negative phrases ("Not less than").
Problem: It is long assumed that negation in quantification negatively affects
the readability of requirements, however, empirical research on these topics
remains sparse. Principal Idea: In a web-based experiment with 51 participants,
we compare the impact of negations and quantifiers on readability in terms of
reading effort, reading error rate and perceived reading difficulty of
requirements. Results: For 5 out of 9 quantifiers, our participants performed
better on the affirmative phrase compared to the negative phrase. Only for one
quantifier, the negative phrase was more effective. Contribution: This research
focuses on creating an empirical understanding of the effect of language in
Requirements Engineering. It furthermore provides concrete advice on how to
phrase requirements.
