Averge and Dispersion

[raheelkhosa]

Below are listed the rates of abortion per 100,000 women for 13 US states in 1973 and 1975. Describe what happened to these distributions over the two- year period. Did the average rate increase or decrease? What happened to the dispersion of this distribution?

State 1973 1975
Maine 3.5 9.5
Massachusetts 10 25.7
New York 53.5 40.7
Pennsylvania 12.1 18.5
Ohio 7.3 17.9
Michigan 18.7 20.3
Iowa 8.8 14.7
Nebraska 7.3 14.3
Hawaii 26.3 31.6
California 30.8 33.6
Arizona 6.9 15.8
Texas 6.8 19.1
Florida 15.8 30.5

i am confused about the question when it is asking what happened to the distribution over two years, than it asking about average. Do i need to take average of whole column of 1973 and 1975.
And the second part what happened to the dispersion of this distribution, i am not sure what do here.
thanks for help.

[raheelkhosa]

so far i tried and i got this i am not sure if its right please verify
1973 mean

X ̅= x1+X2+X3+X4+X5+X6+X7+X8+X9+X10+X11+X12+X13/13
X ̅=3.5+10+53.5+12.1+7.3+18.7+8.8+7.3+26.3+30.8+6.9+6.8+15.8/13
X ̅=207.80/13
X ̅=15.98

1975 mean

X ̅= x1+X2+X3+X4+X5+X6+X7+X8+X9+X10+X11+X12+X13/13
X ̅=9.5+25.7+40.7+18.5+17.9+20.3+14.7+14.3+31.6+33.6+15.8+19.1+30.5
X ̅=292.2/13
X ̅=22.5

The average rate has increased from 15.98 to 22.5.