23.5 Practically significant? A new blend of gasoline costs $1.00 more per gallon than regular gasoline. Tests have shown that gas mileage with the new blend is statistically significantly higher than it is with regular gasoline. The P-value was 0.004. A report about these results goes on to say that the new blend of gasoline increases gas mileage by 2 miles per gallon. Are these results practically significant?

  1. (a) No, because the P-value is small.

  2. (b) No, because a 2 mile-per-gallon increase is probably too small to justify an additional $1.00 per gallon.

  3. (c) Yes, because the P-value is small.

  4. (d) Yes, because a 2 mile-per-gallon increase is bigger than 0.