150%, 1.5 times, 1.5× or 1.5-fold If some measure of quality improves to 150 % of its original value in a study from condition A to condition B, would it be most appropriate, in terms of scientific writing (computer science specifically), to describe that as:



  a 1.5-fold improvement


  a 1.5× improvement


  performing 1.5 times better
The following may seem a bit nitpicking, but such details are what separates the wheat from the chaff:



  a 1.5-fold improvement


Bad. This implies that the improvement – not the quality measure – is 1.5 of something else, that is reasonably comparable, e.g., another improvement. This would make sense in a context like:


  We compared different performance boosters and found that contrafibulaties yielded a 1.5-fold improvement compared to the improvement by pericombobulations.


(Note that I do not consider the above sentence an example of good writing as it is bound to be misunderstood by somebody, but it’s at least technically correct.)

  a 1.5× improvement


Very bad. If I am benign, I read this as “1.5-fold improvement” (see above). If I am not, this does not make any sense at all. Replacing words with mathematical symbols just because they have some semantic relation is a very bad habit as it almost never yields a clear meaning, is bad style, and is indicative of deficiencies in basic mathematical concepts.

  performing 1.5 times better


Meh. If we are being literal, it has problems similar to “a 1.5-fold improvement”: Does 1.5 times apply to better or something else? Now, linguistically, this is a fixed idiom with a clear meaning, so the situation is not that bad, but I would guess that some non-native speakers misunderstand it. Moreover, idioms do not stylistically mix very well with accurate, quantitative descriptions.

  performing 50 % better


Almost Good. Similar to the above, but better, since 50 % is by far not as likely to be understood to apply to better than 1.5 times.

  performing 1.5 times as well
  performing 150 % as well


Good. These leave no room for misunderstanding as you make clear what 1.5 times or 50 % refer to, and it’s the correct thing, namely “goodness”, i.e., your measure of quality.

  an improvement by 50 %
  an improvement to 150 %


Good (with sufficient context). Again, it is clear, what the numbers actually refer to.

  performing 50 % better than A
  performing 1.5 times as well as A
  performing 150 % as well as A
  an improvement by 50 % in comparison to A
  an improvement to 150 % of A’s performance


Very Good. By naming the actual reference, you avoid misunderstandings. However, with sufficient context, the expressions I labelled good may be preferable for brevity and avoiding unnecessary redundancy.


Note that all this assumes a measure of quality that increases with quality. If your measure decreases with quality (e.g., runtime), it’s probably best to directly talk about the measure, e.g.:


  A’s runtime was 50 % of B’s.
  A runs twice as fast as B.