Answer:
67 and 70
Step-by-step explanation:
Mean grade (μ) = 79.7
Standard deviation (σ) = 9.7
D: Scores below the top 83% and above the bottom 9%, which means scores between the 9th and 17th percentile.
z-score at the 9th percentile: -1.34
z-score at the 17th percentile: -0.955
The lower limit of a D grade is:
[tex]-1.34=\frac{L-\mu}{\sigma}\\-1.34=\frac{L-79.7}{9.7}\\ L=66.7[/tex]
The upper limit of a D grade is:
[tex]-0.955=\frac{U-\mu}{\sigma}\\-0.955=\frac{U-79.7}{9.7}\\ L=70.4[/tex]
Rounding to the nearest whole number, the limits for a D grade are 67 and 70.
