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Quick Randomizing. Here's a quick and easy way to randomize. You have 100 subjects: 50 adults under the age of 65 and 50 who are 65 or older. Toss a coin. If it's heads, assign all the adults under the age of 65 to the treatment group and all those 65 and over to the control group. If the coin comes up tails, assign all those 65 and over to treatment and all those under the age of 65 to the control group. This gives every individual subject a \(50-50\) chance of being assigned to treatment or control. Why isn't this a good way to randomly assign subjects to treatment groups?

Short Answer

Expert verified
This method introduces age-related bias due to non-random assignment within age groups.

Step by step solution

01

Understand the Coin Toss Method

In this exercise, a coin is tossed to decide group assignments. If the result is heads, all adults under 65 go to the treatment group, and all those 65 or over go to the control group. If tails, the assignments switch, with those 65 or over in treatment and under 65 in control.
02

Recognize Bias in Coin Toss Method

This method appears fair because both outcomes are equally likely, thus giving a 50% chance of being in a treatment or control group. However, it does not truly randomize individual assignment because assignment is determined solely based on age category, introducing bias.
03

Identify Lack of True Randomization

The problem with this method is that it fails to randomize within age groups. All members of a specific age group are assigned to the same group, either treatment or control. This could introduce confounding factors related to age.
04

Evaluate the Impact of Non-Random Assignment

This lack of individual randomization compromises the experiment's validity. Any observed effects might be attributed to the age-related bias rather than the treatment itself, as each complete age group is treated as a homogeneous unit.

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Key Concepts

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

Randomization
Randomization is a crucial process in randomized controlled trials. It ensures that every participant has an equal opportunity of being placed in any group within the study, such as a treatment group or a control group. This process minimizes selection bias and helps establish a robust cause-and-effect relationship between variables. In the context of the exercise, a proper randomization method would involve assigning each of the 100 subjects independently of their age group to either the treatment or control group. This could be achieved using a random number generator or a lottery system, ensuring that external factors, such as age, do not influence the trial's outcome. Randomization maximizes the likelihood that differences in outcomes between the groups can be attributed to the treatment rather than preconceived biases or external factors.
Bias
Bias refers to systematic error or prejudice in results or inferences. In scientific studies, reducing bias is essential to obtain accurate, valid results. The coin toss method described in the exercise introduces bias because it systematically assigns groups based on age rather than individual characteristics or pure chance. This approach favors one outcome over another related to factors other than the treatment being studied. The result is that the findings from such a study could be inaccurate, as any perceived treatment effect might actually be due to this systematic bias. To reduce bias, individual randomization should be implemented, ensuring that assignments are not influenced by predefined categories, like age.
Confounding Factors
Confounding factors are variables that can affect both the dependent and independent variables, obscuring the true relationship between them. In the context of a study, confounding factors can skew results, making it difficult to determine the real effect of the treatment. The coin toss method introduced confounding factors by grouping individuals strictly by age category. If age imposes its own influence on the treatment's efficacy, results will not accurately reflect the treatment's true impact. To mitigate this, researchers must employ techniques that prevent confounding, such as stratified randomization or adjusting for confounding factors in result analysis, ensuring that any measured outcomes are due solely to the treatment, not to these external factors.
Treatment Group
A treatment group consists of subjects receiving the experimental treatment or intervention in a clinical trial. Their outcomes are compared against those of a control group, which does not receive the treatment. In the discussed exercise, the flawed coin toss method could potentially result in treatment groups that are not comparable due to age sorting, compromising the study's results. Ideally, a treatment group should be a representative sample of the population, with randomization ensuring that the group is not overly influenced by any one characteristic, such as age. When groups are correctly randomized, researchers can be more confident that differences observed are due to the treatment itself, lending credibility to the study's conclusions.

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Most popular questions from this chapter

Eggs and Cholesterol. An article in a medical journal reports on an experiment to see the effect on cholesterol levels of eating three whole eggs per day compared to eating the equivalent of a yolk-free egg substitute. The article describes the experiment as a randomized, single-blinded experiment of 37 subjects with metabolic syndrome. \(\frac{17}{}\) What do you think "single- blinded" means here? Why isn't a doubleblind experiment possible?

Let Them Eat Chocolate. There is some evidence that cocoa has beneficial effects on heart health. To study this, researchers decide to give subjects either a cocoa pill or a placebo daily for a two-year period. Measurements of the subjects' heart health, based on a questionnaire, before and after the two-year period, are to be compared. ? a. Out line the design of this experiment, using 20 subjects, with 10 assigned to each group b. Here are the names of the 20 subjects. Use software or Table B at line 129 to carry out the randomization your design requires. \begin{tabular}{|l|l|l|l|l|} \hline Abel & Devore & Kennedy & Reichert & Stout \\ \hline Aeffner & Fleming & Lamone & Riddle & Williams \\ \hline Birkel & Fritz & Mani & Sawant & Wilson \\ \hline Bower & Giriunas & Mattos & Scannell & Worbis \\ \hline \end{tabular} c. Do you think this can be run as a double-blind experiment? Explain.

Migraine is a prevalent disease characterized by headaches that are often severe and throbbing and accompanied by associated symptoms, such as nausea, vomiting, vertigo, and cognitive dysfunction. A drug, fremanezumab, may be an effective preventive treatment for migraine. To investigate this, researchers give 20 migraine sufferers fremanezumab and observe whether the number of migraine days in a 12 -week period is reduced. This is a. an observational study. b. an uncontrolled experiment. c. a randomized comparative experiment.

Better Sleep? Is the number of times you awaken during the night affected by whet her you have a glass of wine before bed and whether you have a snack before you go to bed? Describe briefly the design of an experiment with two explanatory variables-whether or not you have a glass of wine and whether or not you have a snack before going to bed -to investigate this question. Be sure to specify what the response variable will be. Also tell how you will handle lurking variables such as amount of sleep the previous night.

The Community Intervention Trial for Smoking Cessation asked whether a community-wide advertising campaign would reduce smoking. The researchers located 11 pairs of communities, with each pair similar in location, size, economic status, and so on. One community in each pair was chosen at random to participate in the advertising campaign and the other was not. This is a. an observational study. b. a matched pairs experiment. c. a completely randomized experiment.

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