# STAT 213 Chapter Notes - Chapter 5: Random Variable, Quartile, High Iq Society

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Published on 24 Jun 2019

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Chapter 4: Continuous Random Variables

1. The time, X, it takes a commuter bus to complete its route is uniformly

distributed between 75 and 111 minutes.

A. The density function is:

B. What is the probability that the bus finishes its route in less than

90 minutes?

C. What is the probability the bus takes less than 90 or more than 95

minutes to complete the route?

D. What is the first quartile in this distribution?

Chapter 4: Continuous Random Variables

2.

A. The scores of adults on an IQ test are approximately Normal with

mean 100 and standard deviation 15. The organization MENSA, which

calls itself 'the high IQ society', requires an IQ score of 130 or

higher for membership. About what percent of adults would qualify

for membership?!

B. The proportion of observations from standard Normal distribution

that take values larger than z = -0.75 is about:

C. The proportion of observations from standard Normal distribution

that takes values less than z = 1.15 is about:!

Chapter 4: Continuous Random Variables

3. Pam took 4 courses last semester: Physics, Spanish, Calculus, and

Biology. The means and standard deviations for the final exams, and Pam's

scores are given in the table below. Convert Pam's scores into z-scores.

On what exam did Pam have the highest relative score?

4. Find the z-score from a standard normal distribution that satisfies each

of the following statements.

A. The point!z!with 15.15 percent of the observations falling below

it.!

B. The closest point!z!with 24.54 percent of the observations falling

above it.!