sampler vs mixed bag

sampler and mixed bag both are nouns.

Word	Noun	Adjective	Verb	Adverb
sampler	Yes	No	No	No
mixed bag	Yes	No	No	No

As nouns, mixed bag is a hypernym of sampler; that is, mixed bag is a word with a broader meaning than sampler:

sampler (noun)	mixed bag (noun)
a piece of embroidery demonstrating skill with various stitches	a collection containing a variety of sorts of things
an observation station that is set up to make sample observations of something
an assortment of various samples
someone who samples food or drink for its quality