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Chapter 3: Problem 6

Identify whether each situation describes an observational study or an experiment. If it is an experiment. a. Subjects are asked to run a mile and record their time. b. Fifty students were asked to go to a quiet space in the library to memorize a poem. Fifty students were asked to go to a noisy location in the cafeteria to memorize the poem. Each student recorded how much time it took to memorize the poem.

Short Answer

Expert verified
(a) Observational Study, (b) Experiment.

Step by step solution

01

Define Observational Study and Experiment

An **observational study** is a study where researchers observe subjects and measure variables of interest without assigning treatments to the subjects. An **experiment**, on the other hand, involves the application of a treatment to some subjects and then observing the effects on a response variable.
02

Analyze Situation (a)

In this situation, subjects are asked to run a mile and record their time. The researcher observes the mile times without manipulating any variables or applying any treatment. Therefore, this is an **observational study**.
03

Analyze Situation (b)

In this situation, the researcher assigns fifty students to a quiet space and another fifty to a noisy location, effectively applying a treatment (quiet versus noisy environment) to each group and then records the outcomes. This design involves manipulation and control, which categorizes it as an **experiment**.

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Key Concepts

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

Observational Study
An observational study explores how variables interact with each other through mere observation. Researchers do not attempt to control or change the variables in any way. They simply record and analyze data from what naturally occurs. This type of study is crucial when direct intervention is impractical or unethical.

There are several characteristics of observational studies that set them apart:
  • Non-intrusive: Researchers do not disrupt the normal behavior of subjects.
  • Lack of manipulation: No treatments or interventions are applied to the subjects. They continue with their usual activities.
  • Focus on correlation: Observational studies can identify relationships between variables but cannot establish causation.
Imagine researchers observing how students perform in exams when they follow different study schedules, without altering these schedules themselves. This passive approach helps in understanding natural trends and associations.
Experiment
An experiment involves actively manipulating one or more variables to observe the effect on another variable. Researchers in an experiment apply treatments and keep conditions controlled to determine cause-and-effect relationships.

Experiments typically include the following characteristics:
  • Manipulation: Researchers decide and apply specific treatments to the subjects.
  • Control: Conditions are maintained, and variables are isolated to prevent external factors from affecting the results.
  • Randomization: Subjects may be randomly assigned to treatment groups to eliminate bias.
For instance, in a study where students are asked to memorize a poem in varying noise conditions, the noise environment is a controlled variable, which allows researchers to analyze its influence on memorization compared to another controlled scenario.
Variables in Research
Variables are the building blocks of research; they represent the factors that are measured, manipulated, or controlled in a study. Understanding variables is key to designing and interpreting both observational studies and experiments.

**Types of Variables**
  • Independent Variable: The factor that is manipulated or categorized; for example, the type of environment (quiet or noisy) where students memorize a poem.
  • Dependent Variable: The outcome or result that is measured. In our example, it could be the time taken to memorize the poem.
  • Controlled Variable: Aspects that are kept constant to ensure that changes in the dependent variable are solely due to the independent variable, such as the length of the poem or time limits for memorization.
By clearly defining these variables, researchers can better understand their data, accurately enter conclusions, and precisely determine the validity of their study's findings.

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Most popular questions from this chapter

Identify the sampling method. Just the name will suffice. a. Researchers select every 5 th customer who walks into the store to take a survey. b. Raffle tickets are distributed and collected in a bag, where they are mixed and ten are drawn for prizes. c. I asked the shoppers near me in the shoe department what size they wear. d. An IRS auditor randomly selects 25 taxpayers in each filing status (single, head of household, married filing jointly, and married filing separately).

An experiment compared the ability of three groups of participants to remember briefly-presented chess positions. The data are shown below. The numbers represent the average number of pieces correctly remembered from three chess positions. a. Find the standard deviation of each group. b. Calculate the 5 -number summary for each group. c. Calculate the range and IQR for each group. d. Create side-by-side boxplots and compare and contrast the two groups. $$ \begin{array}{|c|c|c|} \hline \text { Non-players } & \text { Beginners } & \text { Tournament Players } \\ \hline 22.1 & 32.5 & 40.1 \\ \hline 22.3 & 37.1 & 45.6 \\ \hline 26.2 & 39.1 & 51.2 \\ \hline 29.6 & 40.5 & 56.4 \\ \hline 31.7 & 45.5 & 58.1 \\ \hline 33.5 & 51.3 & 71.1 \\ \hline 38.9 & 52.6 & 74.9 \\ \hline 39.7 & 55.7 & 75.9 \\ \hline 39.7 & 55.7 & 75.9 \\ \hline 43.2 & 55.9 & 80.3 \\ \hline 43.2 & 57.7 & 85.3 \\ \hline \end{array} $$

In a 2010 survey, US teens aged \(12-18\) were asked what their favorite movie genre was. The results are shown below. \- Action: 351 \- Adventure: 171 \- Comedy: 651 \- Drama: 389 \- Horror: 287 \- Romance: 107 \- Undecided: 51 a. What is the implied population? b. How many people were sampled? c. What type of data is this? d. Create a relative frequency bar chart of the results. e. Create a pie chart of the results. f. Explain the advantages/disadvantages of the two charts. g. What is the statistic for the percentage of teens whose favorite movie genre is horror?

A study is conducted to determine whether people learn better with routine or crammed studying. Subjects volunteer from an introductory psychology class. At the beginning of the semester 12 subjects volunteer and are assigned to the routine studying group. At the end of the semester 12 subjects volunteer and are assigned to the crammed studying group. a. Identify the target population and the sample. b. Is this an observational study or an experiment? c. This study involves two kinds of non-random sampling: 1. Subjects are not randomly sampled from a specified population and 2. Subjects are not randomly assigned to groups. Which problem is more serious? What effect on the results does each have?

CNN conducted a survey of 500 American adults. \(62 \%\) of those surveyed answered yes to the question, "Do you favor a law to ban the sale of assault weapons and semiautomatic rifles?" The reported margin of error was \(\pm 4 \%\) a. What population is being studied? b. What is the sample? c. What type of data is this? d. Is the \(62 \%\) reported in the problem an example of a statistic or a parameter? e. What is the confidence interval? Is the confidence interval about the statistic or the parameter? f. Explain what the confidence interval tells you.
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