Box averages and SDs are unknown. Null says the two box averages are equal. Alternative says the '98 box has a higher average. Not statistically significant. Null says the calculators have no effect.
Alternative says calculators hurt.
If the null is true, expect the difference between the two percents to be 0 give or take 4.17. Can't be done. The observed average in the county sample is 402. Alternative says the county average is lower. The observed average in the county sample is 402.