Answer:
0.0968 = 9.68% probability that the mean number of flaws exceeds 1.9 per square yard.
Step-by-step explanation:
Normal probability distribution
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.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean and standard deviation , the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean and standard deviation .
In this problem, we have that:
Use the central limit theorem to find the approximate probability that the mean number of flaws exceeds 1.9 per square yard.
This is 1 subtracted by the pvalue of Z when X = 1.9. So
By the Central Limit Theorem
has a pvalue of 0.9032
1 - 0.9032 = 0.0968
0.0968 = 9.68% probability that the mean number of flaws exceeds 1.9 per square yard.