I disagree. The common reading of .5 bigger is \(\displaystyle 50\%\text{ bigger }\)
Or \(\displaystyle \text{Larger by }50\%\) or even half again as large.
The whole phrase is ".5 bigger than the original."
This suggests .5 larger than the original, or .5 in addition to the original.
Example:
.5 bigger than 3 =
.5 larger than 3 =
.5 greater than 3 =
3 + .5 =
3.5
Then, again, I would classify that phrase, ".5 bigger than"
as ambiguous/meaningless.
As I see it (in my example), 3 is a number that is increased by another number
("another number" here being .5).
But 50% is a ratio.
So 3 + 50% is meaningless.
The common reading of "50% bigger than the original"
should mean "50% larger than the original,"
but .5 and 50% are not interchangeable, as the former is (sometimes) a number to the latter,
which is a ratio and also a non-number.
Here's another example:
1 bigger than 3 =
1 more than 3 =
3 + 1 =
4
But,
100% bigger than 3 =
larger by 100% of 3 =
3 + (100%)(3) =
3 + 3 =
6
