Question

According to the article "Rubbing Hands Together Under Warm Air Dryers Can Counteract Bacteria Reduction" (Infectious Disease News, September 22,2010 ), washing your hands isn't enough-good "hand hygiene" also includes drying hands thoroughly. The article described an experiment to compare bacteria reduction for three different hand-drying methods. In this experiment, subjects handled uncooked chicken for 45 seconds, then washed their hands with a single squirt of soap for 60 seconds, and then used one of the three hand-drying methods. The bacteria count on their hands was then measured. Suppose you want to carry out a similar experiment with 30 subjects who are willing to participate. Describe a method for randomly assigning each of the 30 subjects to one of the hand-drying methods.

Short answer

First, 30 unique labels are created, each representing a subject in the experiment. These labels are thoroughly mixed in a container to ensure randomness. Hand-drying methods are then assigned to subjects by drawing one label at a time and assigning that subject to a method. This is repeated until all labels are drawn, resulting in each method being tested on 10 subjects. This method ensures the randomness and absence of bias in the assignment of subjects.

Step-by-step solution

Understand the Scenario

The experiment consists of 30 subjects and 3 hand-drying methods. So, each method is to be tested on an equal number of subjects. The total number of subjects 30 is evenly divisible by the number of groups 3 (i.e., 30/3 = 10). Thus, each hand-drying method will be tested on 10 subjects.

Prepare Subject Labels

Create 30 identical labels, each representing a subject in the experiment. Each label will have a unique subject identifier.

Randomize Subject Assignments

Put all the 30 labels in a container and shuffle them to randomize their order. Then, draw a label one by one for each hand-drying method. Repeat this process until there are no labels left in the container.

Assure Randomness

Following this method, every subject has an equal chance of being assigned to each of the hand-drying methods as the process is devoid of bias, satisfying the condition for randomness.

Key concepts

Randomized Experiment

A randomized experiment is a cornerstone of statistical research used to infer causality between treatment and outcome. Imagine you are conducting a study to understand the effectiveness of different hand-drying methods in reducing bacterial count. To ensure that the results of the study are reliable, it is crucial to assign subjects to hand-drying methods randomly. This process helps to eliminate selection bias and confounding variables that could skew the results.

For the experiment described, where 30 subjects are divided evenly among three hand-drying methods, randomization could be achieved by assigning each subject a number from 1 to 30. These numbered labels are placed into a container and mixed thoroughly. You would then draw labels without looking to assign 10 subjects to each method. This random allocation is essential because it balances out other variables that might affect hand hygiene, such as age, gender, or prior exposure to bacteria, ensuring that the comparison between hand-drying methods is fair and scientifically valid.

Bacteria Reduction in Hand-Drying Methods

Hand-drying is an integral part of hand hygiene. After washing, hands may still carry bacteria that can be further reduced through effective drying. There are various methods of hand-drying, including paper towels, warm air dryers, and cloth towels, each claiming different levels of bacteria reduction efficacies.

Scientific experiments are conducted to evaluate these claims. The goal is to ascertain which method most effectively minimizes bacterial presence on the hands. In studies like the one described in the exercise, subjects' hands are contaminated and then washed, followed by drying with one of the methods being tested. The reduction in bacteria is measured, which shows the effectiveness of each drying method. It is important to use a standardized process for contaminating and washing hands in order to have a proper baseline for comparison. Additionally, the drying time and technique should be consistent across all methods to ensure that the results reflect the true efficacy of the drying methods themselves and not other variables.

Hand Hygiene Experiment

Conducting a hand hygiene experiment involves more than just the act of drying hands; it begins with a controlled contamination process followed by a standardized method of handwashing. In the experiment from the scenario, subjects handle uncooked chicken, which is known to contain bacteria, to ensure their hands are contaminated. They then wash their hands using a fixed amount of soap and for a set duration, standardizing the cleaning process.

After washing, the hand-drying methods are tested. The bacteria count is measured both before and after drying to determine the reduction in bacteria levels. The experiment's design aims to create a controlled environment that is as close to real-world scenarios as possible while eliminating variables that could affect the outcome. By standardizing each stage and conducting the experiment under strict conditions, researchers can draw meaningful conclusions about the best hand-drying method to reduce bacterial count and, by extension, improve hand hygiene practices.