The word regression is a noun. It cannot be an adjective. When it is paired with another noun, it is a noun adjunct.Examples:"In statistics, regression analysis refers to techniques for modeling and...
"He was a real Alaskan man, though to her knowledge, he'd never been farther north then Nebraska."Another answer (using 'Alaska', as specified, rather than 'Alaskan'):'They experienced a real Alaska...
As a noun: The freestyle skiing demonstrators showed some amazing aerials. The aerial mounted on the media truck broadcast the event all over the country.As an adjective: The aerial performers were...