The BestEver credit scores are normally distributed with a mean of 600 and a standard deviation of 100.
1. What is the probability that a randomly person has a BestEver credit score between 500 and 700?
2. Find the 90th percentile of the BestEver credit score distribution.
3. If a random sample of 100 people is selected, what is the standard deviation of the sample mean BestEver credit scores?