1. A research study examined the blood vitamin D levels of the entire US population of landscape gardeners. The population average level of vitamin D in US landscapers was found to be 35.41 ng/mL with a standard deviation of 4.245 ng/mL. Assuming the true distribution of blood vitamin D levels follows a normal distribution, what is the upper value of the region for which approximately 99.9% of the data are located within the distribution? Recall the 68-95-99.9% observation discussed in the "Normal Distribution" section of the textbook that is helpful in answering the
2. A research study examined the blood vitamin D levels of the entire US population of landscape gardeners. The population average level of vitamin D in US landscapers was found to be 53.16 ng/mL with a standard deviation of 5.364 ng/mL. Assuming the true distribution of blood vitamin D levels follows a normal distribution, if you randomly select a landscaper in the US, what is the probability that his/her vitamin D level will be 47.00 ng/mL or less?