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_name_18 (best_fit__all_data_ VARCHAR, parameter VARCHAR)

### Question ###
What is the best fit (all data) when the parameter shows fluctuation amplitude at 8h −1 mpc?

### Accurate SQL ###

SELECT best_fit__all_data_ FROM table_name_18 WHERE parameter = "fluctuation amplitude at 8h −1 mpc"