An experiment was conducted to compare the mean reaction times to two types of traffic signs: prohibitive (No Left Turn) and permissive (Left Turn Only). Ten drivers were included in the experiment. Each driver was presented with 40 traffic signs, 20 prohibitive and 20 permissive, in random order. The mean time to reaction (in milliseconds) was recorded for each driver and is shown here.

a. Explain why this is a paired-difference experiment and give reasons why the pairing should be useful in increasing information on the difference between the mean reaction times to prohibitive and permissive traffic signs.
b. Use the Excel printout to determine whether there is a significant difference in mean reaction times to prohibitive and permissive traffic signs. Use the p-value approach.

Driver Prohibitive Permissive 702 725 744 824 866 841 770 929 764 857 831 846 759 792 708 747 685 742 610 10 t-Test: Paired Two Sample for Means Prohibitive Permissive 818.7 1573.344444 10 0.693852753 0 9 9.14983257 3.72891E-06 1.833112933 7.45782E-06 2.262157163 711.8 2596.4 10 Mean Variance Observations Pearson Correlation Hypothesized Mean Difference df t Stat P(Tt) one-tail t Critical one-tail P(Tt) two-tail t Critical two-tail