 |
| ||
| |||
|
| Math Central | Quandaries & Queries |
|
Question from Ammara: Hi, I'm trying to figure out how a paper I'm looking at has found a percentage from the numbers below. its a paper comparing two lenses. it says that the new lenses 'slowed the progression of refractive error by approximately 50%'. the refractive error with the old lenses was -2.26 after two years it was -3.28 the refractive error with the new lenses was -2.24 after two years the refractive error is - 2.75 Thank you so much for your help it is most appreciated! |
Hi Ammara,
The method for calculating percentage change is described in our response to an earlier question.
For the old lenses I think that in the paper you are reading they take the earlier measurement to be 2.26 and the later to be 3.28 so the calculation is
\[\frac{3.28 - 2.26}{2.26} = \frac{1.02}{2.26} = 0.4513 \mbox{ or } 45.13 \%.\]
For the new lens the calculation gives
\[\frac{2.75 - 2.24}{2.26} = \frac{0.51}{2.26} = 0.2377 \mbox{ or } 23.77 \%.\]
Since 23.77% is approximately one half of 45.13% I think the authors feel they can say that "the new lenses 'slowed the progression of refractive error by approximately 50%'".
I hope this helps,
Penny
| ||
| ||
| ||
 |
 |
|
Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.