A medical device company knows that the percentage of patients experiencing injection-site reactions with the current needle is 11%. What is the standard deviation of X, the number of patients seen until an injection-site reaction occurs? 3.1289 8.5763 9.0909 11

The two word phrase could be:  "For Every"

When we are writing a ratio or fraction, we are comparing two different quantities. 

Imagine that a track athlete has to run 3 miles for every day of practice. We could write the ratio 3:1.

Imagine that your parents are going to pay you $15 for every A on your report card. We could write the ratio 15:1

The key words are "For Every".