Answer:
n = 98, that is, she scored at the 98th percentile.
Step-by-step explanation:
When the distribution is normal, we use the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
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.
In this question, we have that:
She scored 38, so
Test scores are normally distributed with a mean of 25 and a standard deviation of 6.4.
This means that
Find the percentile:
We have to find the pvalue of Z. So
has a pvalue of 0.98(rounding to two decimal places).
So n = 98, that is, she scored at the 98th percentile.