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Chapter 2: Problem 82

Researchers at the University of Houston decided to test the hypothesis that restaurant servers who squat to the level of their customers would receive a larger tip ("Effect of Server Posture on Restaurant Tipping." Journal of Applied Social Psychology [1993]: \(678-685)\). In the experiment, the waiter would flip a coin to determine whether he would stand or squat next to the table. The waiter would record the amount of the bill and of the tip and whether he stood or squatted. a. Describe the treatments and the response variable. b. Discuss possible extraneous variables and how they could be controlled. c. Discuss whether blocking would be necessary. d. Identify possible confounding variables. e. Discuss the role of random assignment in this experiment.

Short Answer

Expert verified
The treatments are the waiter's two postures - standing and squatting, and the response variable is the tip received. Extraneous variables such as the waiter's demeanor, food quality, and timing could be controlled by maintaining consistency. Blocking may be needed if certain groups of customers react differently to server posture, and confounding variables could include type of meal, location of the table, and customer's mood. Random assignment, via a coin flip, is crucial to ensure a representative sample and minimize confounding variables.

Step by step solution

01

Identify Treatments and Response Variable

The treatments in this experiment are the two different postures of the server: standing or squatting. The response variable is the tip size that the server receives.
02

Identify and Control Extraneous Variables

Extraneous variables may include the demeanor of the waiter, the quality of the food, the time of day or week, or the personality of the customer. These could be controlled by ensuring that the waiter behaves consistently across all customers, the quality of the food is consistent, and the experiment is conducted at various time intervals.
03

Discuss the Necessity of Blocking

Blocking may or may not be necessary in this experiment. If there are groups of customers that are expected to react differently to server posture, then blocking would be advantageous to even out the effect of these groups on the response.
04

Identify Possible Confounding Variables

Some possible confounding variables include the type of meal ordered by customers (fancy or plain), the location of the table (quiet or noisy area), and customer mood during the meal.
05

Discuss the Role of Random Assignment

Random assignment is important in this experiment to ensure that both treatments (squatting and standing) are applied to a representative sample of customers, thus minimizing the impact of confounding variables. The coin flip used to decide whether the server will stand or squat is a form of random assignment.

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Key Concepts

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

Response Variable
In this experiment, the response variable is the size of the tip that the waiter receives. This is the key outcome researchers are interested in measuring. Essentially, the response variable is what they want to understand or predict in relation to the different treatments being applied.

For example, by altering the server's posture (either standing or squatting), researchers aim to see if there is a significant change or pattern in the tip amounts from the customers.
  • It captures the effect of the server's posture on customer behavior.
  • This variable is measured after the treatment to provide data for analysis.
Understanding the response variable helps in analyzing the effectiveness of an experiment and drawing valid conclusions from it.
Extraneous Variables
Extraneous variables are those additional factors that are not the focus of the study, yet they can influence the outcome.

In this tipping experiment, several extraneous variables could affect tipping behavior, such as the demeanor of the waiter, the quality of the food, or even the time of day.
  • The waiter's mood or level of engagement might affect tips, irrespective of their posture.
  • The quality or promptness of the meal can also sway customer generosity.
  • Dining during busy hours might lead to different tipping than quieter periods.
To mitigate their impact, it鈥檚 essential to control these variables as much as possible, ensuring consistency. This can be achieved by maintaining the same quality of service and food throughout the study, and varying the time and place of the observation equitably.
Confounding Variables
Confounding variables are those that the experimenters might not initially spot, but can muddle the results by being closely linked to both the independent and dependent variables.

For this restaurant experiment, possible confounding variables might include the type of meal ordered, the location of the table, or the customer鈥檚 mood.
  • Higher-priced meals may lead customers to tip more, regardless of server posture.
  • A table in a noisy or uncomfortable location might lead to lower tips, skewing results.
  • Customers' moods, influenced by factors beyond the server鈥檚 posture, could alter their tipping behavior.
Identifying and controlling for confounding variables is crucial to accurately assess the effect of different server postures on tipping, leading to more reliable conclusions.
Random Assignment
Random assignment is a cornerstone of experimental design, crucial for minimizing bias and ensuring reliable results. In this experiment, random assignment was achieved through the waiter flipping a coin to decide whether to stand or squat.

Random assignment is important because:
  • It ensures that both the standing and squatting postures are applied across a diverse range of customer groups.
  • This variability helps in balancing out any unforeseen influences on the response variable, making the results more generalizable.
  • It reduces the impact of confounding variables by distributing them statistically evenly across treatment groups, leading to a fair comparison between postures.
Using a method like a coin flip achieves a simple yet effective randomization, crucial for the integrity of the study and the validity of its findings.

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Most popular questions from this chapter

The article "Effects of Too Much TV Can Be Undone" (USA Today, October 1, 2007) included the following paragraph: Researchers at Johns Hopkins Bloomberg School of Public Health report that it's not only how many hours children spend in front of the \(\mathrm{TV},\) but at what age they watch that matters. They analyzed data from a national survey in which parents of 2707 children were interviewed first when the children were \(30-33\) months old and again when they were \(5 \frac{1}{2}\), about their TV viewing and their behavior. a. Is the study described an observational study or an experiment? b. The article says that data from a sample of 2707 parents were used in the study. What other information about the sample would you want in order to evaluate the study? c. The actual paper referred to by the USA Today article was "Children's Television Exposure and Behavioral and Social Outcomes at 5.5 years: Does Timing of Exposure Matter?" (Pediatrics [2007]: 762-769). The paper describes the sample as follows: The study sample included 2707 children whose mothers completed telephone interviews at both 30 to 33 months and 5.5 years and reported television exposure at both time points. Of those completing both interviewers, 41 children \((1 \%)\) were excluded because of missing data on television exposure at one or both time points. Compared with those enrolled in the HS clinical trial, parents in the study sample were disproportionately older, white, more educate, and married. The "HS clinical trial" referred to in the excerpt from the paper was a nationally representative sample used in the Healthy Steps for Young Children national evaluation. Based on the above description of the study sample, do you think that it is reasonable to regard the sample as representative of parents of all children at age 5.5 years? Explain. d. The USA Today article also includes the following summary paragraph: The study did not examine what the children watched and can't show TV was the cause of later problems, but it does "tell parents that even if kids are watching TV early in life, and they stop, it could reduce the risk for behavioral and social problems later," Mistry says. What potentially confounding variable is identified in this passage? e. The passage in Part (d) says that the study cannot show that TV was the cause of later problems. Is the quote from Kamila Mistry (one of the study authors) in the passage consistent with the statement about cause? Explain.

To examine the effect of exercise on body composition, healthy women age 35 to 50 were classified as either active \((9\) hours or more of physical activity per week) or sedentary (鈥淓ffects of Habitual Physical Activity on the Resting Metabolic Rates and Body Composition of Women aged 35 to 50 Years," Journal of the American Dietetic Association [2001]: \(1181-1191\) ). Percent body fat was measured and the researchers found that percent body fat was significantly lower for women who were active than for sedentary women. a. Is the study described an experiment? If so, what are the explanatory variable and the response variable? If not, explain why it is not an experiment. b. From this study alone, is it reasonable to conclude that physical activity is the cause of the observed difference in body fat percentage? Justify your answer.

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The article "Display of Health Risk Behaviors on MySpace by Adolescents" (Archives of Pediatrics and Adolescent Medicine [2009]:27-34) described a study in which researchers looked at a random sample of 500 publicly accessible MySpace web profiles posted by 18-year-olds. The content of each profile was analyzed. One of the conclusions reported was that displaying sport or hobby involvement was associated with decreased references to risky behavior (sexual references or references to substance abuse or violence). a. Is the study described an observational study or an experiment? b. Is it reasonable to generalize the stated conclusion to all 18 -year-olds with a publicly accessible MySpace web profile? What aspect of the study supports your answer? c. Not all MySpace users have a publicly accessible profile. Is it reasonable to generalize the stated conclusion to all 18-year-old MySpace users? Explain. d. Is it reasonable to generalize the stated conclusion to all MySpace users with a publicly accessible profile? Explain.
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