# Normal Distribution and Z-Tests Review: Statistics

I’m stuck on a Statistics question and need an explanation.

The following questions are what I am stuck on for a review for an exam for a statistics course. I am trying to understand the concepts so please be clear with the explanation/make the work easy to follow. Z-scores are attached. Typed or handwritten is fine. Thanks!

Normal Distribution and Z-Tests (see attached for values):

6) A Z-score value of +1.25 corresponds to an area of 0.3944. What does this mean in words?

7) A population of 820 students took a standardized test. The distribution of test scores was normally distributed with a mean of 62 and a variance of 36. You scored a 70. How many standard normal deviates away from the mean is your score?

8) Given the same conditions as in question 7, how many students scored below you on this test?

10) The level of creatinine in a person’s blood is variable. The standard deviation of creatinine level in blood is 0.35, and the mean creatinine level of a patient measured on 20 different days was 9.75mg/dL. Estimate a 95% confidence interval of the blood creatinine level of this patient.