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4.67 The hospital is planning a new emergency-room facility. It wants enough beds in the emergency ward so that for at least \(95 \%\) of normal-pollution days it will not need to turn anyone away. What is the smallest number of beds it should have to satisfy this criterion? The hospital also finds that on high-pollution days the number of admissions is Poisson-distributed with mean \(=4.0\) admissions per day. Answer Problem 4.67 for highpollution days.

Short Answer

Expert verified
The hospital should have at least 7 beds for high-pollution days.

Step by step solution

01

Understand the Problem

The hospital wants to ensure it has enough beds on normal-pollution days so it doesn't turn away patients at least 95% of the time. We will assume a probability distribution for the number of admissions per day. On high-pollution days, admissions follow a Poisson distribution with a mean of 4.
02

Decide on a Distribution Assumption

For normal-pollution days, typically we assume admissions also follow a Poisson distribution but with a different mean, which is not given. We'll solve the problem first for high-pollution days, as they involve specific information given in the problem.
03

Determine the Criterion for High-Pollution Days

We need to calculate the number of beds needed to cover admissions 95% of the time. The number of admissions per day is Poisson distributed with a mean of 4.
04

Use Poisson Distribution Formula

For a Poisson process with mean \( \lambda = 4 \), the probability of \( k \) admissions is given by: \[ P(X = k) = \frac{e^{-\lambda} \cdot \lambda^k}{k!} \] where \( e \) is the base of the natural logarithm.
05

Build Cumulative Distribution Function (CDF)

Calculate the CDF (cumulative distribution) to find the least number of beds, \( n \), such that \( P(X \leq n) \geq 0.95 \). Compute cumulative probabilities for successive values of \( n \) until the condition is met.
06

Calculate Cumulative Probabilities

Calculate \( CDF(n) = P(X \leq n) \) stops when \( CDF(n) \geq 0.95 \). We do this using the Poisson probabilities for each value from 0 to \( n \).
07

Find Minimum Number of Beds

By calculation or using statistical tables/software, find the smallest \( n \) such that the cumulative probability \( P(X \leq n) \geq 0.95 \). For \( \lambda = 4 \), the smallest \( n \) is 7.

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Key Concepts

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

Emergency Room Planning
Planning an emergency room requires careful consideration of the number of patients it might serve. The goal is to have enough resources, such as beds, to meet patient demand effectively. For instance, in a scenario where the hospital aims to accommodate patients on at least 95% of days, it must estimate patient inflow realistically.
To make such predictions, hospitals often rely on historical data and statistical methods. This helps in understanding the variability and patterns in patient admissions. Proper planning helps in minimizing the risk of overcrowding, ensuring that emergency services remain efficient even during peak times. Determining the appropriate number of beds is a vital step in this planning, and statistical tools like probability distributions become quite handy in this task.
Probability Distribution
Probability distribution is a cornerstone concept in statistics, describing how the probabilities are distributed across different potential outcomes. In the context of emergency room admissions, this involves predicting how many patients might be admitted on any given day.
The probability distribution chosen for modeling admissions depends on the type of data usually collected. The Poisson distribution is a common choice for modeling counts, such as the number of admissions, because it helps in understanding the frequency of events within a fixed period.
  • This distribution works best for events that happen independently and with a known average rate.
  • It's required to decide on this type of distribution before moving forward with further calculations.
Having an appropriate probability distribution is crucial for accurate planning and resource allocation.
Cumulative Distribution Function
The cumulative distribution function (CDF) is a powerful tool in statistics. It helps determine the probability that a random variable takes a value less than or equal to a specific threshold.
In our emergency room scenario, using the CDF allows the hospital to calculate the number of beds needed to ensure that they can accommodate patients most of the time—specifically, 95% of the time.
  • For a Poisson-distributed random variable, the CDF is calculated by summing up probabilities from zero admissions up to a certain number, \( n \).
  • We continue this until the cumulative probability meets or exceeds 0.95.
This threshold helps determine the minimum number of resources, such as beds, required to meet the planning goal. Using the CDF contributes significantly to efficient hospital management by giving insights into resource demand.
Hospital Admissions
Hospital admissions are a fundamental aspect of healthcare service planning. The number of admissions gives an insight into resource needs, which helps in preparing for both normal and exceptional situations like high-pollution days.
These admissions often follow a predictable pattern that statistical distributions can model.
  • Understanding these patterns helps hospitals manage their capacity effectively.
  • Reliable data on admissions allows for effective use of statistical tools, which optimize the number of available beds and other resources.
Efficient management of hospital admissions can lead to improved patient care and decreased wait times, ensuring a better overall healthcare experience for patients. Thus, accurate modeling and planning based on historical admission data are vital for the hospital's operational efficiency.

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Most popular questions from this chapter

An experiment is designed to test the potency of a drug on 20 rats. Previous animal studies have shown that a \(10-\mathrm{mg}\) dose of the drug is lethal \(5 \%\) of the time within the first 4 hours; of the animals alive at 4 hours, \(10 \%\) will die in the next 4 hours. What is the probability that 1 rat will die in the 8-hour period?

The presence of bacteria in a urine sample (bacteriuria) is sometimes associated with symptoms of kidney disease in women. Suppose a determination of bacteriuria has been made over a large population of women at one point in time and \(5 \%\) of those sampled are positive for bacteriuria. Suppose 100 women from this population are sampled. What is the probability that 3 or more of them are positive for bacteriuria?

Suppose we want to check the accuracy of self-reported diagnoses of angina by getting further medical records on a subset of the cases. If we have 50 reported cases of angina and we want to select 5 for further review, then how many ways can we select these cases if order of selection matters?

Suppose the number of admissions to the emergency room at a small hospital follows a Poisson distribution but the incidence rate changes on different days of the week. On a weekday there are on average two admissions per day, while on a weekend day there is on average one admission per day. What is the probability of having 0, 1, and 2+ admissions for an entire week, if the results for different days during the week are assumed to be independent?

Some previous studies have shown a relationship between emergency-room admissions per day and level of pollution on a given day. A small local hospital finds that the number of admissions to the emergency ward on a single day ordinarily (unless there is unusually high pollution) follows a Poisson distribution with mean \(=2.0\) admissions per day. Suppose each admitted person to the emergency ward stays there for exactly 1 day and is then discharged. On a random day during the year, what is the probability there will be 4 admissions to the emergency ward, assuming there are 345 normal-pollution days and 20 high-pollution days?

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