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Minimum latency depends on forwarding performance of each switch, bandwidth of each port, congestion, cut-through or store-and-forward forwarding, size of frame, distance between switches, and number of hops. Since you also mentioned a 3750 stack, depth of stack would also likely impact latency.
However, on non-congested 2960 <> 3750 stack <> 2960, as the other posters have noted, you're latency is likely to be under a millisecond.
PS:
BTW, normal pings between hosts wasn't designed for high timing accuracy.
