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Ch. 4 - Probability
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Non è quello che usi tu?Cambia libro di testo
Capitolo 4, Problema 4.4.24a

ATM You want to obtain cash by using an ATM, but it’s dark and you can’t see your card when you insert it. The card must be inserted with the front side up and the printing configured so that the beginning of your name enters first.


a. What is the probability of selecting a random position and inserting the card with the result that the card is inserted correctly?

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Step 1: Understand the problem. The card can be inserted in four possible orientations: (1) front side up with the beginning of the name entering first, (2) front side up with the end of the name entering first, (3) back side up with the beginning of the name entering first, and (4) back side up with the end of the name entering first.
Step 2: Identify the favorable outcome. The card is inserted correctly only if it is front side up and the beginning of the name enters first. This is one specific orientation out of the four possible orientations.
Step 3: Calculate the total number of possible outcomes. Since there are four possible orientations for inserting the card, the total number of outcomes is 4.
Step 4: Calculate the probability of the favorable outcome. The probability is given by the formula: \( P = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} \). Substitute the values: \( P = \frac{1}{4} \).
Step 5: Conclude that the probability of inserting the card correctly is \( \frac{1}{4} \), which represents one favorable outcome out of four possible orientations.

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Probability

Probability is a measure of the likelihood that a particular event will occur, expressed as a number between 0 and 1. In this context, it refers to the chance of inserting the ATM card correctly based on the possible orientations of the card. Understanding how to calculate probability involves recognizing the total number of favorable outcomes over the total number of possible outcomes.
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Introduction to Probability

Random Selection

Random selection refers to choosing an item or position without any bias or predetermined criteria. In the ATM scenario, it implies that the position where the card is inserted is chosen randomly, which affects the probability of the card being inserted correctly. This concept is crucial for determining how many ways the card can be inserted and how many of those ways are correct.
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Intro to Random Variables & Probability Distributions

Outcomes

Outcomes are the possible results of a random experiment. In this case, the outcomes are the different ways the ATM card can be inserted, which include both correct and incorrect orientations. Identifying all possible outcomes is essential for calculating the probability of a successful insertion, as it helps in determining the ratio of favorable outcomes to total outcomes.
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The Binomial Experiment
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In Exercises 1–10, use the data in the accompanying table and express all results in decimal form. (The data are from “The Left-Handed: Their Sinister History,” by Elaine Fowler Costas, Education Resources Information Center, Paper 399519.)


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Both Lefties If two of the study subjects are randomly selected with replacement, find the probability that they both write with their left hand.

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Florida Pick 3 In the Florida Pick 3 lottery, you can place a “straight” bet of \$1 by selecting the exact order of three digits between 0 and 9 inclusive (with repetition allowed), so the probability of winning is 1/1000. If the same three numbers are drawn in the same order, you collect \$500, so your net profit is \$499.


a. Find the actual odds against winning.

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Testing for Marijuana Use


a. How many subjects are included in the study?

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Denomination Effect

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Denomination Effect


a. Find the probability of randomly selecting a student who kept the money, given that the student was given four quarters.

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Vision Correction About 75% of the U.S. population uses some type of vision correction (such as glasses or contact lenses).


b. If four different people are randomly selected, what is the probability that they all use vision correction?

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Finding Odds in Roulette A roulette wheel has 38 slots. One slot is 0, another is 00, and the others are numbered 1 through 36, respectively. You place a bet that the outcome is an odd number.


a. What is your probability of winning?

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