MATH30 - Long Quiz #2 - 3rd TERM - 20112012


I.               MULTIPLE CHOICE
The following statements are vital in strengthening your discernment on aspects of decision making through the process of PROBABILITY AND STATISTICS. Write TRUE if the statement suffices affirmation that substantiates the claims while FALSE if the statement nullifies the assertions. (2 points each)

1.       The measure of voltage for a smoke detector battery can be any value between 0 volts and 9 volts. It is therefore a discrete random variable.
2.       A probability distribution gives the probability for each value of the random variable.
3.       The count of the number of patrons viewing a movie is finite number and is therefore a continuous random variable.
4.       The requirements for a discrete probability distribution are 0 p(x) 1 and   1.
5.       Toss two fair coins and let x equal the number of heads observed. HH appears one in eight.
6.       The Poisson distribution provides a simple, easy-to-compute, and accurate information to binomial probabilities when n is large and np is small.
7.       A binomial experiment consists of n identical trials with probability of success p on each trial.
8.       The probability density function f(x), defined over the set of real numbers, has a total probability value which is greater than one.
9.       The cumulative distribution F(x) of a continuous random variable X with density function f(x) has P(X x).
10.    The joint probability distribution is a situation when probability distribution of random variables’ simultaneous occurrence can be represented by f(x, y) for any pair of values (x, y).
11.    The f(x, y) is a joint density function of the continuous random variables X and Y if it has probability equal to one f(x, y) 0.
12.    The population mean is the value that you would expect to observe if the experiment is repeated over and over again.
13.    The normal approximation is appropriate for binomial random variable.
14.    The probability distribution can either be discrete or continuous.
15.    There must be only two possible outcomes for Poisson probability distribution.

II.             PROBLEM SOLVING
The decision making process can be applied in a variety of everyday situations and across most academic disciplines. In the following applications, you are going to execute what you relatively understood from the fundamental analysis.

1.       Over a long period of time, it has been observed that a professional basketball player can make on a given trial with probability equal to 0.80. Suppose he shoots four free throws, what is the probability that he will make at least one free throw? (5 points)
2.       The average number of traffic accidents on a certain section of highway is two per week. Determine the probability of at most three accidents on this section of highway during a two-week period. (5 points)
3.       QGC bids on a job to construct a building. If the bid is won, there is a 0.70 probability of making a Php 7,500,000.00 profit and there is a probability of 0.30 that the contractor will break even. What is the expected value? Should the bid be submitted? (10 points)
4.       For what value of k, f(x, y) represents the probability density function of two continuous random variables X and Y, where
f(x, y) =         (10 points)
5.       A random variable X has the following probability function. Find P(x ≤ 4).

X
0
1
2
3
4
5
6
7
P(X)
0
k
2k
2k
3k
k2
2k2
7k2 + k
(10 points)
6.       Suppose that you must establish regulations concerning the maximum number of people who can occupy the elevator. A study of elevator occupancies indicates that if eight people occupy the elevator, the probability distribution of the total weight of the eight people has a mean equal to 1200 pounds and a standard deviation of 99 pounds. What is the probability that the total weight of eight people exceeds 1300 pounds? 1500 pounds? Assume that the distribution is approximately normal. (10 points)
7.       The reliability of the strength of concrete is the probability that a concrete specimen, chosen at random from production will function under its designed conditions. Random samples of 100 concrete specimens were tested. With the compressive strength reliability of 0.98, calculate the mean and standard deviation of the under conditioned strength of the specimens. (10 points)
8.       On the exam for Civil Engineers, scores are normally distributed with a mean of 615 and a standard deviation of 107. If an institution requires scores above the 70TH percentile for entering Master of Science in Structural Engineering, determine the cut-off point. (10 points)

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