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2 answers:
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Answer:
95.64% probability that pledges are received within 40 days
Step-by-step explanation:
Problems of normally distributed samples are solved using 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 problem, we have that:
What is the probability that pledges are received within 40 days
This is the pvalue of Z when X = 40. So
has a pvalue of 0.9564
95.64% probability that pledges are received within 40 days
For this case we must find the product of the following expression:
We combine using the product rule for radicals:
So, we have:
We rewrite the 216 as
By definition of properties of powers and roots we have:
Then, the expression is:
Answer:
Option D