Which technique would be useful for each of the following situations?

a. To rank-order the causes of a quality problem.

b. To brainstorm the reasons why a product might have failed.

c. To find an assignable cause.

d. To determine if a process range is under control.

e. To reduce the variability of failures found in the field under actual use of the product.

f. To achieve the smallest possible variance in the time it takes to wait on tables in a restaurant.