Multiple choice questions from random variables

1) A test consists of 690 true or false questions. If the student guesses on each question, what is the mean number of correct answers?

A) 0 B) 138 C) 345 D) 690

2) IQ test scores are normally distributed with a mean of 101 and a standard deviation of 13. An individual's IQ score is found to be 103. Find the z-score corresponding to this value.

A) 0.15 B) 6.50 C) -0.15 D) -6.50

3) The length of time it takes college students to find a parking spot in the library parking lot follows a normal distribution with a mean of 4.0 minutes and a standard deviation of 1 minute. Find the probability that a randomly selected college student will take between 2.5 and 5.0 minutes to find a parking spot in the library lot.

A) .4938 B) .7745 C) .0919 D) .2255

4) In a recent survey, 61% of the community favored building a police substation in their neighborhood. If 14 citizens are chosen, find the probability that exactly 5 of them favor the building of the police substation.

A) 0.211 B) 0.357 C) 0.035 D) 0.610

5) True or False: The proportion of the population that has certain characteristics is the same as the probability that a randomly selected individual of the population has these same characteristics.

A) True B) False

6) For a standard normal curve, find the z-score that separates the bottom 70% from the top 30%.

A) 0.52 B) 0.12 C) 0.47 D) 0.98

7) A lab orders a shipment of 100 rats a week, 52 weeks a year, from a rat supplier for experiments that the lab conducts. Prices for each weekly shipment of rats follow the distribution below:

Price $10.00 $12.50 $15.00
Probability 0.25 0.4 0.35

Suppose the mean cost of the rats turned out to be $12.75 per week. Interpret this value.

A) The rat cost that occurs more often than any other is $12.75.
B) Most of the weeks resulted in rat costs of $12.75.
C) The average cost for all weekly rat purchases is $12.75.
D) The median cost for the distribution of rat costs is $12.75.

8) The amount of corn chips dispensed into a 32-ounce bag by the dispensing machine has been identified as possessing a normal distribution with a mean of 32.5 ounces and a standard deviation of 0.2 ounce. What chip amount represents the 67th percentile for the bag weight distribution?

A) 32.63 ounces B) 32.09 ounces C) 32.59 ounces D) 32.13 ounces

9) Which of the below is not a requirement for binomial experiment?

A) The probability of success is fixed for each trial of the experiment.
B) For each trial there are two mutually exclusive outcomes.
C) The trials are mutually exclusive.
D) The experiment is performed a fixed number of times.

10) The area under a standard normal density curve with mean of 0 and standard deviation of 1 is

A) ? + 2(3ô???) B) Infinite C) 1 D) ? + 3ô???

11) A test consists of 10 multiple choice questions, each with five possible answers, one of which is correct. To pass the test a student must get 60% or better on the test. If a student randomly guesses, what is the probability that the student will pass the test?

A) 0.377 B) 0.060 C) 0.205 D) 0.006

12) The length of time it takes college students to find a parking spot in the library parking lot follows a normal distribution with a mean of 3.5 minutes and a standard deviation of 1 minute. Find the probability that a randomly selected college student will find a parking spot in the library parking lot in less than 3.0 minutes.

A) .3085 B) .2674 C) .3551 D) .1915