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Chapter 1: Problem 44

Indicate whether the study is an observational study or a controlled experiment. A local public school encourages, but does not require, students to wear uniforms. The principal of the school compares the grade point averages (GPAs) of students at this school who wear uniforms with the GPAs of those who do not wear uniforms to determine whether those wearing uniforms tend to have higher GPAs.

Short Answer

Expert verified
The study is an observational study.

Step by step solution

01

Identify Variables

In the given problem, the independent variable is the decision of students on whether to wear a uniform or not. The dependent variable is their gained GPA.
02

Identify Control Type

Now it is crucial to understand if this is a controlled experiment or an observational study. We need to determine if a deliberate intervention or treatment has been applied on the independent variable (wearing or not wearing uniforms). In our case, the decision of wearing or not wearing uniforms is taken by the students themselves and not imposed as part of the experiment.
03

Classification of the Study

Since there's no deliberate intervention in the study, and the researcher is only observing the variables with no control on their conditions, the study is classified as an observational study.

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Key Concepts

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

Independent Variable
In any study or experiment, the **independent variable** is a crucial element because it is the variable that you change or control to see how it affects other variables. In an observational study, you don't manipulate the independent variable. You just observe how it naturally varies and affects the dependent variable.
In the problem at hand, the independent variable is whether or not the students choose to wear uniforms. It is called "independent" because it is supposed to remain uninfluenced by other variables in the study, even though in reality, other uncontrolled factors may still affect it.
Understanding the role of independent variables helps researchers and observers distinguish between causes and effects within different conditions.
Controlled Experiment
A **controlled experiment** is characterized by researchers having control over all variables except for the one being tested, which is the independent variable. This type of experiment allows researchers to establish cause and effect because they can manipulate the independent variable and observe its direct impact on the dependent variable.
In the exercise, there is no controlled experiment because the students who wore uniforms or didn't were not assigned by anyone conducting the study. Such a lack of control indicates that no deliberate intervention or treatment occurs on the independent variable.
  • Researchers use controlled experiments to isolate the effects of an independent variable efficiently.
  • By having a control group and a test group, they minimize the effects of external factors.
Understanding these differences can help recognize why some study results can be more conclusive than others.
Dependent Variable
The **dependent variable** is what you measure in the experiment or study. It is the variable that is affected during the experiment, providing data for analysis about how the independent variable influences it.
In the provided problem, the dependent variable is the students' GPAs. The researchers want to see if there is a difference in GPAs between students who wear and who do not wear uniforms. By observing the dependent variable, researchers hope to determine its relationship to the independent variable.
By understanding and correctly identifying the dependent variable, you can better analyze if changes in the independent variable lead to changes in this measured outcome.

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Most popular questions from this chapter

Indicate whether the study is an observational study or a controlled experiment. A group of boys is randomly divided into two groups. One group watches violent cartoons for one hour, and the other group watches cartoons without violence for one hour. The boys are then observed to see how many violent actions they take in the next two hours, and the two groups are compared.

Snacks Emmanuel, a student at a Los Angeles high school, kept track of the calorie content of all the snacks he ate for one week. He also took note of whether the snack was mostly "sweet" or "salty." The sweet snacks: \(90,310,500,500,600,90\) The salty snacks: \(150,600,500,550\) Write these data as they might appear in (a) stacked format with codes and (b) unstacked format.

Association between Glycemic Load and Acne? An article in the Journal of the Academy of Nutrition and Dietetics reported on a study of diet in subjects with moderate to severe acne. Read the excerpts from the abstract and answer the questions that follow. (Source: Burris et al., "Differences in dietary glycemic load and hormones in New York City adults with no or moderate/severe acne," Journal of the Academy of Nutrition and Dietetics, vol. 117 [September 2017]: \(1375-1383\) ) Methods: Sixty-four participants (no acne, \(\mathrm{n}=32\); moderate/severe acne, \(\mathrm{n}=32\) ) were included in this study. Participants completed a 5 -day food record, had blood drawn and completed a questionnaire to evaluate food-aggravated acne beliefs and acne-specific quality of life. Results: Participants with moderate/severe acne consumed greater total carbohydrate compared to participants without acne. Participants with moderate/severe acne had greater insulin compared to participants without acne. Although there were no differences between groups, \(61 \%\) of participants reported food-influenced acne. a. Was this a controlled experiment or an observational study? Explain how you know. b. Assuming the study was properly conducted, can we conclude that higher consumption of carbohydrates causes more severe acne? Explain.

Incarceration Rates (Example 7) The table gives the prison population and total population for a sample of states in 2014-15. (Source: The 2017 World Almanac and Book of Facts) $$ \begin{array}{|l|c|c|} \hline \text { State } & \text { Prison Population } & \text { Total Population } \\ \hline \text { California } & 136,088 & 39,144,818 \\ \hline \text { New York } & 52,518 & 19,795,791 \\ \hline \text { Illinois } & 48,278 & 12,859,995 \\ \hline \text { Louisiana } & 38,030 & 4,670,724 \\ \hline \text { Mississippi } & 18,793 & 2,992,333 \\ \hline \end{array} $$ Find the number of people in prison per thousand residents in each state and rank each state from the highest rate (rank 1\()\) to the lowest rank (rank 6). Compare these rankings of rates with the ranks of total numbers of people in prison. Of the states in this table, which state has the highest prison population? Which state has the highest rate of imprisonment? Explain why these two answers are different.

In a 2017 study designed to investigate the effects of exercise on secondlanguage learning, 40 subjects were randomly assigned to one of two conditions: an experimental group that engaged in simultaneous physical activity while learning vocabulary in a second language and a control group that learned the vocabulary in a static learning environment. Researchers found that learning second-language vocabulary while engaged in physical activity led to higher performance than learning in a static environment. (Source: Liu et al., "It takes biking to learn: Physical activity improves learning a second language," PLoS One, May 18,2017, https://doi.org/10.1371/journal. pone.0177624) a. What features of a well-designed controlled experiment does this study have? Which features are missing? b. Assuming that the study was properly conducted, can we conclude that the physical activity while learning caused the higher performance in learning second-language vocabulary? Explain.
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