Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_222448_1 (percent_defective VARCHAR, sigma__with_15σ_shift_ VARCHAR)

### Question ###
When sigma (with 1.5σ shift) is 2.5, what percent is defective?

### Accurate SQL ###

SELECT percent_defective FROM table_222448_1 WHERE sigma__with_15σ_shift_ = "2.5"