After reading the chapter for these question, I am still having a hard time. I need some explinations please.

1. What exact percent of the normal curve falls between the mean and -3 to +3 standard deviations from the mean? (Hint: the correct answer is not 100% meaning no need to round the number) 2. What exact percent falls the normal curve falls below at Z score of -2.00? (Hint: The answer is not 95% meaning not need to round the number). 3. How does the normal curve allow behavioral scientists to compare different types of scales, tests and instruments (Hint: please think Z scores for full credit!). How does understanding probability help us understand statistics