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A cola-dispensing machine is set to dispense on average 7.00 ounces of cola per cup. The standard deviation is 0.10 ounces. The distribution amounts dispensed follows a normal distribution. a. What is the probability that the machine will dispense between 7.10 and 7.25 ounces of cola? b. What is the probability that the machine will dispense 7.25 ounces of cola or more? c. What is the probability that the machine will dispense between 6.80 and 7.25 ounces of cola?

Short Answer

Expert verified
a) 0.1525 b) 0.0062 c) 0.9710

Step by step solution

01

Understand the Problem

We are given that the cola dispensing machine dispenses amounts following a normal distribution with a mean \( \mu = 7.00 \) ounces and a standard deviation \( \sigma = 0.10 \) ounces. We need to find the probabilities for different specified ranges of dispensed amounts.
02

Convert to Z-scores

Use the formula for the Z-score: \( Z = \frac{X - \mu}{\sigma} \). Convert the specified dispensing amounts into Z-scores.- For 7.10 ounces: \( Z = \frac{7.10 - 7.00}{0.10} = 1 \).- For 7.25 ounces: \( Z = \frac{7.25 - 7.00}{0.10} = 2.5 \).- For 6.80 ounces: \( Z = \frac{6.80 - 7.00}{0.10} = -2 \).
03

Find Z-score Probabilities from Normal Distribution Table

Use the standard normal distribution table to find the probabilities for the Z-scores. - Probability that Z < 1: Approximate cumulative probability is 0.8413. - Probability that Z < 2.5: Approximate cumulative probability is 0.9938. - Probability that Z < -2: Approximate cumulative probability is 0.0228.
04

Calculate Probability for Part (a)

To find the probability that the machine dispenses between 7.10 and 7.25 ounces:\( P(1 < Z < 2.5) = P(Z < 2.5) - P(Z < 1) = 0.9938 - 0.8413 = 0.1525 \).
05

Calculate Probability for Part (b)

To find the probability that the machine dispenses 7.25 ounces or more:\( P(Z > 2.5) = 1 - P(Z < 2.5) = 1 - 0.9938 = 0.0062 \).
06

Calculate Probability for Part (c)

To find the probability that the machine dispenses between 6.80 and 7.25 ounces:\( P(-2 < Z < 2.5) = P(Z < 2.5) - P(Z < -2) = 0.9938 - 0.0228 = 0.971 \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Z-score calculation
To understand how a cola-dispensing machine's output can be analyzed, we first need to delve into the concept of a Z-score. A Z-score, in statistics, is a measure that describes a value's position relative to the mean of a group of values. It is expressed in terms of standard deviations from the mean.Here's how you calculate a Z-score:- Use the formula: \[ Z = \frac{X - \mu}{\sigma} \] Where: - \(X\) is the value you are reporting - \(\mu\) is the mean of the distribution - \(\sigma\) is the standard deviationFor the cola machine, different Z-scores help us find the probabilities related to dispensing amounts. For example, to find the Z-score for the value 7.10 ounces:- Calculate: \[ Z = \frac{7.10 - 7.00}{0.10} = 1 \]This conversion allows us to look up probabilities in the standard normal distribution table, which tells us what proportion of data falls below (or above) this Z-score. Remember, Z-score conversion makes it easier to calculate probabilities for values in any normally distributed dataset.
Probability in statistics
Probability is the language of uncertainty in statistics, helping us quantify the likelihood of events. When dealing with a normal distribution, such as the amount of cola dispensed by a machine, probabilities give insights about the chance of certain outcomes occurring.To tackle probability calculations:- We use the Z-scores derived from our data points.- Look up these Z-scores in the standard normal distribution table.- The table provides cumulative probabilities, which show the chance that a value is less than or equal to a given Z-score.For example:- To find the probability that the machine dispenses between 7.10 and 7.25 ounces, calculate the difference between the cumulative probabilities at Z = 1 and Z = 2.5: \[ P(1 < Z < 2.5) = P(Z < 2.5) - P(Z < 1) = 0.9938 - 0.8413 = 0.1525 \]The result, 0.1525, indicates a 15.25% probability.Probability helps make informed decisions about where our data points are likely to be, based on historical data.
Standard deviation
Standard deviation is a crucial concept in statistics, representing the amount of variation or dispersion in a set of values. In simpler terms, it tells us how much the values in a dataset typically differ from the mean. Why is standard deviation important? - It gives a common measure of consistency in a dataset. - For the cola machine setup, the standard deviation of 0.10 ounces indicates the variability around the mean amount of 7.00 ounces. - A smaller standard deviation indicates the data points are close to the mean, while a larger one suggests more spread out data points. Calculating Z-scores uses standard deviation, as it scales the difference between a value and the mean into a standardized unit. This scaling is vital to apply the concept of a normal distribution uniformly, regardless of the original scale of data units.

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Most popular questions from this chapter

The monthly sales of mufflers in the Richmond, Virginia, area follow the normal distribution with a mean of 1,200 and a standard deviation of \(225 .\) The manufacturer would like to establish inventory levels such that there is only a 5 percent chance of running out of stock. Where should the manufacturer set the inventory levels?

A recent article in the Cincinnati Enquirer reported that the mean labor cost to repair a heat pump is \(\$ 90\) with a standard deviation of \(\$ 22 .\) Monte's Plumbing and Heating Service completed repairs on two heat pumps this morning. The labor cost for the first was \(\$ 75\) and it was \(\$ 100\) for the second. Compute \(z\) values for each and comment on your findings.

A uniform distribution is defined over the interval from 6 to \(10 .\) a. What are the values for a and \(b\) ? b. What is the mean of this uniform distribution? c. What is the standard deviation? d. Show that the total area is 1.00 . e. Find the probability of a value more than 7 . f. Find the probability of a value between 7 and \(9 .\)

A normal population has a mean of 20.0 and a standard deviation of \(4.0 .\) a. Compute the \(z\) value associated with 25.0 . b. What proportion of the population is between 20.0 and \(25.0 ?\) c. What proportion of the population is less than \(18.0 ?\)

America West Airlines reports the flight time from Los Angeles International Airport to Las Vegas is 1 hour and 5 minutes, or 65 minutes. Suppose the actual flying time is uniformly distributed between 60 and 70 minutes. a. Show a graph of the continuous probability distribution. b. What is the mean flight time? What is the variance of the flight times? c. What is the probability the flight time is less than 68 minutes? d. What is the probability the flight takes more than 64 minutes?

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