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Chapter 1: Problem 11

The article "How Dangerous Is a Day in the Hospital?" (Medical Care [2011]: 1068-1075) describes a study to determine if the risk of an infection is related to the length of a hospital stay. The researchers looked at a large number of hospitalized patients and compared the proportions who got an infection for two groups of patients-those who were hospitalized overnight and those who were hospitalized for more than one night. Indicate whether the study is an observational study or an experiment. Give a brief explanation for your choice.

Short Answer

Expert verified
The study described is an observational study because the researchers simply observed and recorded the variables of interest (infection rate and length of hospital stay) without intervening or manipulating any factors. They compared the infection rates between two naturally occurring groups of patients without altering their treatments or randomly assigning them to different groups.

Step by step solution

01

Understanding definitions of observational study and experiment

In an observational study, the researcher observes and records the variables of interest without intervening or manipulating any factor. On the other hand, in an experiment, the researcher actively manipulates one or more variables, assigns subjects randomly to different treatments or control groups, and then observes the effect of that manipulation on the outcome variable(s). #Step 2: Comparing the study with the definitions#
02

Comparing the study with the definitions

In the given study, researchers looked at a large number of hospitalized patients and compared the proportions who got an infection for two groups of patients - those who were hospitalized overnight and those who were hospitalized for more than one night. The researchers did not manipulate any factors or treatments. #Step 3: Identify the study type and provide explanation#
03

Identify the study type and provide explanation

Based on the definitions and the procedure used in the study, we can conclude that the study is an observational study. This is because the researchers observed and recorded the variables of interest (infection rate and length of hospital stay) without intervening or manipulating any factors. They compared the infection rates between two naturally occurring groups of patients without altering their treatments or randomly assigning them to different groups.

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Key Concepts

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

Infection Rates
Understanding infection rates is crucial, especially in hospital settings where patients are vulnerable. Infection rates refer to the frequency at which infections occur within a specific population over a certain period of time. In a hospital, this could mean the number of patients acquiring infections from the health facility itself. Several factors can influence these rates, such as the sterility of medical equipment, the frequency of staff washing their hands, or even the types of infections common in certain regions. To control infection rates, hospitals might adopt procedures like:
  • Strict hygiene protocols
  • Regular cleaning of rooms and equipment
  • Patient isolation for infectious cases
Understanding the infection rates within a hospital can help in taking the right preventive measures, ultimately protecting patients and reducing their hospital stay duration.
Hospital Stay Duration
Hospital stay duration refers to the number of days a patient spends in a hospital from admission to discharge. This can vary vastly depending on a patient's condition, treatment plan, and overall health. Short stays might be ideal but don't always reflect the level of care needed. Conversely, longer stays can increase the risk of hospital-acquired infections. Thus, balancing the length of stay is key to patient health outcomes. Factors potentially affecting hospital stay duration include:
  • The severity of the patient's illness
  • Type of treatment received
  • Patient's response to the treatment
  • Hospital policies and available medical staff
Managing these factors can help minimize unnecessary extended stays, improving both patient safety and hospital resource use.
Study Design in Statistics
Study design in statistics is the backbone of conducting successful and valid research. Properly designed studies ensure that the collected data serves the research purpose accurately. In the given context, understanding whether the study is observational or experimental is important. Observational studies, like the one in the exercise, involve observing subjects without manipulating any variables. This is key when experiments are not feasible due to ethical or practical reasons. Benefits of statistical studies include:
  • Understanding relationships among variables
  • Identifying trends and patterns over time
  • Helping in decision-making and policy formulation
Statistics facilitate deeper analysis and an evidence-based approach to understanding complex issues, such as infection rates and hospital stay duration. Ensuring that a study's design is appropriate helps unearth true insights, making it a fundamental aspect of scientific research.

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Most popular questions from this chapter

The article "Super Bowls: Serving Bowl Size and Food Consumption" (Journal of the American Medical Association [2005]: \(1727-1728\) ) describes an experiment investigating how the size of serving bowls influences the amount a person eats. In this experiment, graduate students at a university were recruited to attend a Super Bowl party. The paper states that as the students arrived, they were led in an alternating order to one of two identical buffet tables on opposite sides of an adjoining room. The tables had identical amounts of snacks, such as nuts, pretzels, and chips. All of the snacks contained approximately the same number of calories per gram. On one of the tables the snacks were set out in large serving bowls and on the second table the snacks were set out in smaller serving bowls. The students were given a plate and invited to serve themselves before going to another room to watch the game. When they arrived at the game room, their plates were weighed and the number of calories in the food on the plate was estimated. The researchers concluded that serving bowl size does make a difference, with those using large serving bowls tending to take more food. a. Do you think that the alternate assignment to the experimental groups (large serving bowls, small serving bowls) based on arrival time is "close enough" to random assignment? That is, do you think it would tend to create comparable experimental groups? b. In this study, the research assistant who weighed the plates and estimated the calorie content of the food on the plate was blinded as to which experimental group the plate belonged to and was also blinded as to the purpose of the experiment. Why do you think the researchers chose to incorporate this type of blinding?

Researchers at the University of Utah carried out a study to see if the size of the fork used to eat dinner has an effect on how much food is consumed (Food Network Magazine, January 2012). The researchers assigned people to one of two groups. One group ate dinner using a small fork, and the other group ate using a large fork. The researchers found that those who ate with a large fork ate less of the food on the plate than those who ate with the small fork. The title of the article describing this study was "Dieters Should Use a Big Fork." This title implies a cause-and-effect relationship between fork size and amount eaten and also generalizes this finding to the population of dieters. What would you need to know about the study design to determine if the conclusions implied by the headline are reasonable?

A building contractor has a chance to buy an odd lot of 5000 used bricks at an auction. She is interested in determining the proportion of bricks in the lot that are cracked and therefore unusable for her current project, but she does not have enough time to inspect all 5000 bricks. Instead, she checks 100 bricks to determine whether each is cracked. Describe the population and the sample for this problem.

A petition with 500 signatures is submitted to a college's student council. The council president would like to determine what proportion of those who signed the petition are actually registered students at the college. There is not enough time to check all 500 names with the registrar, so the council president decides to select a simple random sample of 30 signatures. Describe the steps in a process she might use to do this.

The article "Rethinking Calcium Supplements" (U.S. Airways Magazine, October 2010) describes a study investigating whether taking calcium supplements increases the risk of heart attack. Consider the following four study descriptions. For each study, answer the following five questions: Question 1: Is the study described an observational study or an experiment? Question 2: Did the study use random selection from some population? Question 3: Did the study use random assignment to experimental groups? Question 4: Based on the study description, would it be reasonable to conclude that taking calcium supplements is the cause of the increased risk of heart attack? Question 5: Would it be reasonable to generalize conclusions from this study to some larger population? If so, what population? Study 1: Every heart attack patient and every patient admitted for an illness other than heart attack during the month of December, 2010 , at a large urban hospital was asked if he or she took calcium supplements. The proportion of heart attack patients who took calcium supplements was significantly higher than the proportion of patients admitted for other illnesses who took calcium supplements. Study 2: Two hundred people were randomly selected from a list of all people living in Minneapolis who receive Social Security. Each person in the sample was asked whether or not they took calcium supplements. These people were followed for 5 years, and whether or not they had had a heart attack during the 5-year period was noted. The proportion of heart attack victims in the group taking calcium supplements was significantly higher than the proportion of heart attack victims in the group not taking calcium supplements. Study 3: Two hundred people were randomly selected from a list of all people living in Minneapolis who receive Social Security. Each person was asked to participate in a statistical study, and all agreed to participate. Those who had no previous history of heart problems were instructed not to take calcium supplements. Those with a previous history of heart problems were instructed to take calcium supplements. The participants were followed for 5 years, and whether or not they had had a heart attack during the 5 -year period was noted. The proportion of heart attack victims in the calcium supplement group was significantly higher than the proportion of heart attack victims in the no calcium supplement group. Study 4: Four hundred people volunteered to participate in a 10-year study. Each volunteer was assigned at random to either group 1 or group \(2 .\) Those in group 1 took a daily calcium supplement. Those in group 2 did not take a calcium supplement. The proportion who suffered a heart attack during the 10 -year study period was noted for each group. The proportion of heart attack victims in group 1 was significantly higher than the proportion of heart attack victims in group 2
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