Respuesta :
Answer:
Test score of 75.7.
Step-by-step explanation:
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 zscore 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 pvalue, we get the probability that the value of the measure is greater than X.
The results are normally distributed with a mean test score of 60 and a standard deviation of 8.
This means that [tex]\mu = 60, \sigma = 8[/tex]
Calculate the test score above which 2.5% of all test scores lie.
Above the 100 - 2.5 = 97.5th percentile, which is the value of X when Z has a pvalue of 0.975, so X when Z = 1.96.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]1.96 = \frac{X - 60}{8}[/tex]
[tex]X - 60 = 8*1.96[/tex]
[tex]X = 75.7[/tex]
Test score of 75.7.
