:2. Solution. 
Chi-square = (1750 - 1800)^2 / 1800  +  (1800 - 1800)^2 / 1800 <p>

+  (250 - 200)^2 / 200 <p>

= 13.9 <p>

The number of degrees of freedom is 3-1 = 2.  Since 13.9 is
bigger than 9.21, the observed signicance level is less than 1%. <p>