AE 09 Probability Concepts

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Questions and Answers

Which of the following best describes the core idea of probability?

  • A complex calculation involving only past events.
  • An absolute guarantee of an event's outcome.
  • A method for precisely predicting future events.
  • A numerical measure of the likelihood that an event will occur. (correct)

Which of the following is the most accurate description of an experiment in the context of probability?

  • A process that generates well-defined outcomes. (correct)
  • A random process without structured results.
  • A process with unpredictable outcomes.
  • A process with only one possible outcome.

In the context of counting rules, what is a multiple-step experiment?

  • An experiment that is repeated multiple times.
  • An experiment described as a sequence of steps. (correct)
  • An experiment with only two possible outcomes.
  • An experiment performed with a single action.

Kentucky Power & Light is starting a project with two stages: design and construction. The design stage can take 2, 3, or 4 months, and construction can take 6, 7, or 8 months. How many possible completion time outcomes are there?

<p>9 (A)</p> Signup and view all the answers

What differentiates combinations from permutations when counting experimental outcomes?

<p>Permutations consider the order of items, while combinations do not. (C)</p> Signup and view all the answers

An inspector needs to select 3 parts out of 8 for inspection. In how many ways can this selection be made if the order of selection does not matter?

<p>56 (A)</p> Signup and view all the answers

What are the two basic requirements for assigning probabilities to experimental outcomes?

<p>Probabilities must be between 0 and 1, and their sum must equal 1. (C)</p> Signup and view all the answers

In assigning probabilities, when is the classical method most appropriate?

<p>When outcomes are equally likely. (C)</p> Signup and view all the answers

When is the 'relative frequency' method most suitable for assigning probabilities?

<p>When data is available to estimate the proportion of time an outcome will occur. (D)</p> Signup and view all the answers

When is the 'subjective method' used to assign probabilities?

<p>When one cannot realistically assume equally likely outcomes and little relevant data are available. (A)</p> Signup and view all the answers

What is the complement of an event?

<p>The event not occurring. (C)</p> Signup and view all the answers

If the probability of event A is 0.3, what is the probability of the complement of A?

<p>0.7 (B)</p> Signup and view all the answers

What does the addition law of probability help determine?

<p>The probability of the union of two events. (B)</p> Signup and view all the answers

Events A and B are mutually exclusive. If P(A) = 0.4 and P(B) = 0.3, what is P(A ∪ B)?

<p>0.7 (C)</p> Signup and view all the answers

In probability theory, what are mutually exclusive events?

<p>Events that cannot occur at the same time. (A)</p> Signup and view all the answers

What does conditional probability measure?

<p>The probability of an event given that another event has occurred. (C)</p> Signup and view all the answers

Given events A and B, if P(A ∩ B) = 0.2 and P(B) = 0.5, what is P(A|B)?

<p>0.4 (A)</p> Signup and view all the answers

Which of the following statements about probability is most accurate?

<p>Probability is a field where outcomes can sometimes defy initial intuition. (C)</p> Signup and view all the answers

In the Monty Hall problem, after you pick a door, the host opens another to reveal a goat. Should you switch doors?

<p>Yes, switching doubles your chances of winning. (A)</p> Signup and view all the answers

A company has 2 assembly lines. Line A produces 60% of the products, with a 4% defect rate. Line B produces 40% with a 2% defect rate. What is the overall probability that a randomly selected item is defective?

<p>3.2% (A)</p> Signup and view all the answers

A weather forecaster states that there is a 70% chance of rain tomorrow. What type of probability assignment is this?

<p>Subjective (A)</p> Signup and view all the answers

In a class of 30 students, 12 are taking statistics, 8 are taking calculus, and 3 are taking both. What is the probability that a randomly selected student is taking either statistics or calculus?

<p>0.57 (B)</p> Signup and view all the answers

In a game, a player rolls a fair six-sided die. What is the probability of rolling an even number?

<p>1/2 (B)</p> Signup and view all the answers

When rolling two fair six-sided dice, what is the probability of obtaining a sum of 7?

<p>1/6 (B)</p> Signup and view all the answers

A bag contains 5 red marbles and 3 blue marbles. If two marbles are drawn without replacement, what is the probability that both are red?

<p>5/14 (D)</p> Signup and view all the answers

What is the formula for computing permutations?

<p>$\frac{n!}{(n-r)!}$ (B)</p> Signup and view all the answers

What is the formula for computing combinations?

<p>$\frac{n!}{r!(n-r)!}$ (D)</p> Signup and view all the answers

In a survey, 60% of people prefer coffee, and 40% prefer tea. Of those who prefer coffee, 70% add sugar. Of those who prefer tea, 30% add sugar. What percentage of all people add sugar to their drink?

<p>42% (D)</p> Signup and view all the answers

A box contains 10 items, 3 of which are defective. If two items are selected at random without replacement, what is the probability that neither item is defective?

<p>7/15 (C)</p> Signup and view all the answers

A company employs 50 people. 30 have a college degree, and 12 have professional certifications, and 5 have both. If an employee is selected at random, what's the probability they have neither a degree nor a certification?

<p>0.18 (D)</p> Signup and view all the answers

If two events A and B are independent, then:

<p>$P(A|B) = P(A)$ (D)</p> Signup and view all the answers

What is the probability of drawing an ace from a standard deck of 52 cards?

<p>1/13 (B)</p> Signup and view all the answers

A game involves spinning a wheel divided into 20 equal sections, numbered 1 to 20. What is the probability that the wheel will stop on a number that is both even and a multiple of 5?

<p>1/10 (A)</p> Signup and view all the answers

A pharmaceutical company is testing a new drug. In clinical trials, 65% of patients showed improvement, 15% experienced side effects, and 8% showed improvement and experienced side effects. What is the probability that a patient showed improvement or experienced side effects?

<p>72% (B)</p> Signup and view all the answers

A survey found that 80% of customers like pizza, 70% like burgers, and 55% like both. What percentage of customers like either pizza or burgers?

<p>95% (C)</p> Signup and view all the answers

In a certain city, 60% of the days are cloudy. What is the probability that a randomly selected day is not cloudy?

<p>0.4 (C)</p> Signup and view all the answers

A company sends out two teams to solicit donations. Team A visits 40% of the households and Team B visits the rest. Team A gets a donation from 5% of the households they visit, while Team B gets a donation from 8%. What is the overall percentage of households that donate?

<p>6.8% (C)</p> Signup and view all the answers

Flashcards

What is Probability?

A numerical measure of how likely an event is to occur.

What is an experiment?

A process that generates well-defined outcomes.

What is the Multiple-Step Experiment Rule?

If an experiment has k steps, with n1, n2, ..., nk possible outcomes respectively, the total number of experimental outcomes is (n1)(n2)...(nk).

What are Combinations?

Formula to count outcomes when selecting r objects from n.

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What are Permutations?

A counting technique that computes experimental outcomes when selecting r objects from n where order is important.

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Probability Requirement 1

Each outcome's probability must be between 0 and 1.

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Probability Requirement 2

Total of all probabilities equals 1.

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What is Classical Method?

Method for assigning probabilities when all experimental outcomes are equally likely.

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What is Relative Frequency Method?

Assigning a probability based on the proportion of times an experimental outcome occurs when the experiment is repeated many times.

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Subjective Method

When probabilities are assigned based on personal judgment.

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What is the Complement of an Event?

The probability that event will not occur.

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Addition Law

The sum of the probabilities.

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What are Mutually Exclusive Events?

When two events cannot occur at the same time.

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Conditional Probability

The probability of an event given that another event has occurred.

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Study Notes

  • AE 09 (Lec) is the course code.
  • Rocelle Ann G. Terco is the facilitator.

Learning Objectives

  • Understand basic probability concepts.
  • Learn various counting rules.
  • Identify ways of assigning probabilities.
  • Familiarize yourself with the basic relationships of probability.

Flow of Session

  • Prelim Exam Review
  • Intro to Probability
  • Counting Rules
  • Basic Relationships of Probability
  • Conditional Probability

Probability Questions

  • Possible questions include the chance of rain, stock increase, heart attack, living past 70, rolling dice doubles, winning the lottery, or becoming a billionaire.

Probability

  • Probability is a numerical measure of the likelihood that an event will occur.
  • Numerical probability ranges from 0-1.

Experiment

  • An experiment is a process that generates well-defined outcomes.
  • Experimental outcomes for tossing a coin are heads or tails.
  • Experimental outcomes for selecting a part for inspection are defective or non-defective.
  • Experimental outcomes for conducting a sales call are purchase or no purchase.
  • Experimental outcomes for rolling a die are 1, 2, 3, 4, 5, 6.
  • Experimental outcomes for playing a football game are win, lose, or tie.
  • The sample space is all the possible outcomes from the experiment.

Multiple-Step Experiments

  • If an experiment involves a sequence of k steps, with n1 possible outcomes on the first step, n2 on the second, and so on, the total number of experimental outcomes is (n1)(n2)...(nk).

Combinations

  • Combinations allow counting the number of experimental outcomes when the experiment involves selecting r objects from a set of n objects.
  • An inspector randomly selects 2 of 5 parts for inspection, there exist 10 possible ways this can happen.
  • A,B,C,D, and E are possible combinations of selected parts.
  • Ultra Lotto 6/58 is a Philippine Charity Sweepstakes Office (PCSO) where six numbers from 1-58 are chosen to play.

Permutations

  • Permutations compute the number of experimental outcomes when the experiment involves selecting r objects from a set of n objects, where order is important.
  • An inspector randomly selects 2 of 5 parts for inspection; there are 20 permutations of 2 parts can be selected.

Assigning Probabilities

  • Each experimental outcome must be between 0 and 1, inclusively.
  • The sum of the probabilities for all the experimental outcomes must be equal to 1.

Classical Method

  • Appropriate when all experimental outcomes are equally likely.

Relative Frequency Method

  • Data is available to estimate when an experimental outcome occurs with a large number of trials.

Subjective Method

  • Appropriate when one cannot realistically assume that the experimental outcomes are equally likely and when little relevant data are available.
  • An analyst estimates the S&P 500 will hit all-time highs at 20% the analyst evaluates trends and current market conditions.

Complement of an Event

  • A purchasing agent states is 90% confidence a supplier will send a shipment that is free of defective parts, we can conclude that there is a 10% probability that the shipment will contain defective parts.

Addition Law

  • At the end of a performance evaluation period, the production manager found that 5 of the 50 workers completed work late, 6 of the 50 workers assembled a defective product, and 2 of the 50 workers both completed work late and assembled a defective product, the probability of this happening is equal to 0.18%.

Mutually Exclusive Events

  • Mutually Exclusive Events means that one or the other event will occur alone.

Conditional Probability

  • This is the possibility of an event or outcome happening, based on the existence of a previous event or outcome.
  • A survey of smartphone users showed that 47% use an iPhone. If 26% of iPhone users are under the age of 25 and 30% of non-iPhone users are under the age of 25, find the probability that someone does not use an iPhone given that the person is aged at least 25 years old.

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