I think I did mention the one from CA Canada, where they had surveyed just under 500 university students, and 94% of them said that trips to science centres, museums, natural history museums, and general science experiences increased their interest in science and technology.
That's one of the more recent studies. I know Tracy can speak to a few.
The ASTC, which is the Association of Science-Technology Centers, based out of the United States, has a binder about this thick in terms of studies that have been done over the last 15 to 20 years.