Difficulty of remembering a series of items

[Troy Kelley]

Anyone out there know of any research that pertains to the difficulty of
remembering a series of unrelated items.  For example, how much harder is
it to recall one item vs three?  Is it just a straight probability?.. you
have a 1/3 chance of remembering one item out of three, and that you have a
1/1 chance of remembering just one?   I would like to incorporate
activation levels into the formula.  So, If they were related items, my
activation levels (through spreading activation) takes that into accout, so
perhaps I can use the same formula as long as I use activation levels?  For
example, suppose I have 3 items with activation levels of .3, .4 and .1..
how much harder is it to remember that than one item with an activation
level of .2?
 
Hope this is clear,
 
Thanks
Troy Kelley