Florida Southern College Random Variable & Wechsler Intelligence Scale Exercises

I’m working on a statistics practice test / quiz and need a reference to help me understand better.

1.The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 65000 miles and a standard deviation of 3100 miles. What is the probability a particular tire of this brand will last longer than 58000 miles?

2.The Wechsler Intelligence Scale for Children is approximately normally distributed, with mean 100 and standard deviation 15. What is the probability that a randomly selected test taker will score below 90?(Round your answer to 4 decimal places)

3.Find the z-score for which the area under the standard normal curve to its left is 0.40

4.Find the z-score for which the area under the standard normal curve to its left is 0.70

5.For a standard normal curve, find the z-score that separates the bottom 90% from the top 10%.

6.Determine the z-score with 28.5% of standard normal curve lying to the left of z. (3 decimal places)

7.Determine the total area under the standard normal curve to the left of z = -0.24 or to the right of z = 1.20. (Round your answer to four decimal places)

8.Use the following graph to find the area of the shaded region. (Round your answer to 4 decimal places)