A racing car driver is investigating whether the type of fuel he uses in his car affects his overall speed. He uses three different types of fuel. The driver runs an experiment where he fills his car with each type of fuel 20 times, and each time records the time taken to drive one lap of a track. A one-way ANOVA test is conducted to test the null hypothesis that type of fuel is not a significant factor in determining speed. The result of the test is that the null hypothesis is not rejected. The conclusion that follows from this test is that:

a. it has been proven that the type of fuel is a significant factor in determining speed
b. it cannot be ruled out that the type of fuel is an insignificant factor in determining speed
c. it has been proven that the type of fuel is an insignificant factor in determining speed
d. it has been proven that the type of fuel can sometimes be a significant factor in determining speed