I am studying statistics in a textbook. I have successfully answers two questions about normal distribution. Here are the questions
Credit scores are three-digit numbers used by lenders when evaluating your credit worthiness
A. Construct a histogram of the credit scores. Do the credit scores appear approximately normally distributed? Explain.
B.Construct a normal probability plot (QQ-plot) of the credit scores. Do the credit scores appear approximately normally distributed? Explain.
C. If your answer in (b) is yes, find the probability that a city will have a credit score of at least 680. Use the sample mean of the data for (miu) , and the sample standard deviation for (s). Here is the data for the questions :
670 705 680 690 653 675 675 655 667 672 707 688 671 688 660 676 686 691 675 693
For questions 1A , i plot a histogram in R and test the normality using Minitab and the statistics test shows that data is normally distributed . 1B also normally distributed. I want to ask how to work on 1C. My work goes this way
SD = (X - Mean) / z
Does my answer from 1a and 1b correct? Because im not sure graphically i found some data out of the straight line. And how can i do 1C for this? im stuck from SD and the Mean