D Question 13 Two professors decided to compare the variance of their grading procedures. To . accomplish this, " they each graded the same 10 exams, with the following results: Mean Grade Standard Deviation Professor 1 79.3 22.4 Professor 2 84.6 18.3 The calculated F ratio is: There is no correct answer 3.180 O 5.352 O 3.484 O 1.498D Question 12 A normal distribution with a mean of zero and a standard deviation of one is: O part of a family of normal curves, each one defined by a specific mean and standard deviation O all answers here are correct O utilized to determine the probability of occurrence of normally distributed events O unique, in that there is only one curve that fits this definition O a symmetric curve for which the median and mode are also equal to zero