Dr. Smith, a biology professor at Bradford University, has decided to give his classes a standar biology exam that is nationally normed. This indicates that the normal distribution is an appropriate approximation for the probability distribution of students' scores on this exam. The probability distribution of students' scores on this standardized exam can be estimated using the normal distribution shown below. Inflection Point 1 Inflection Point 70 78 86 1. State the mean of the distribution of the biology exam scores. 78 2. State the standard deviation of the distribution of the biology exam scores. 8 points Grading Curve Option I Originally, Dr. Smith decides to curve his students' exam grades as follows. Students whose scores are at or above the 90th percentile will receive an A. Students whose scores are in the 80-89th percentiles will receive a B. Students whose scores are in the 70th-79th percentiles will receive a C. Students whose scores are in the 60th-69th percentiles will receive a D. B Students whose scores are below the 60th percentile will receive an F. 3. Find the z-scores that correspond to the following percentiles. 90th percentile 80th percentile 70th percentile 60th percentile 4. Using that information, find the exam scores that correspond to the curved grading scale. Assume that the exam scores range from 0 to 100. (Round to the nearest whole number.) A: B: -100 C: