standard deviation significance & calculation ?s

[Rob]

i started playing in jan. and started logging my results in july. all my play is online, so i just write down how much i start with and the time and update it every hour. here's what i have:

1/2: 44 hours, +$6.81/hr, (3.4 BB), SD $33.17/hr (16.5 BB)
2/4: 196 hrs., +$10.28/hr (2.5 BB), SD $60.42/hr (15 BB)
3/6: 123 hrs., -$0.33/hr, (-.05 BB), SD $72.08/hr (12 BB)

my first ? is, can i draw any conclusions from these #s?

second, i calculate this per hour rather than per session. how much of a diff. does that make?

third, before i started keeping stats (from when i started in jan. until july), i know i was down $1800, since it's all online. not sure of the # of hours. how can i factor that in?

any clarification would be helpful. i've looked at the archives for info on this and for some reason i can't figure it out. thanks, rob