Respuesta :
Answer:
The minimum score required for an A grade is 83.
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the z-score of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Mean of 72.3 and a standard deviation of 8.
This means that [tex]\mu = 72.3, \sigma = 8[/tex]
Find the minimum score required for an A grade.
This is the 100 - 9 = 91th percentile, which is X when Z has a pvalue of 0.91, so X when Z = 1.34.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]1.34 = \frac{X - 72.3}{8}[/tex]
[tex]X - 72.3 = 1.34*8[/tex]
[tex]X = 83[/tex]
The minimum score required for an A grade is 83.
