91Ó°ÊÓ

Researchers want to know if there is a link between hypertension (high blood pressure) and consumption of salt. Past studies have indicated that the consumption of fruits and vegetables offsets the negative impact of salt consumption. It is also known that there is quite a bit of person-to-person variability in the ability of the body to process and eliminate salt. However, no method exists for identifying individuals who have a higher ability to process salt. The U.S. Department of Agriculture recommends that daily intake of salt should not exceed 2400 milligrams (mg). The researchers want to keep the design simple, so they choose to conduct their study using a completely randomized design. (a) What is the response variable in the study? (b) Name three factors that have been identified. (c) For each factor identified, determine whether the variable can be controlled or cannot be controlled. If a factor cannot be controlled, what should be done to reduce variability in the response variable? (d) How many treatments would you recommend? Why?

Step by step solution

01

Identify the Response Variable

The response variable is what the researchers are measuring or observing as an outcome of the study. In this case, the response variable is the incidence of hypertension (high blood pressure).

02

Identify Factors

Identify the factors that have been mentioned in the study. The factors are as follows: 1. Salt consumption, 2. Consumption of fruits and vegetables, 3. Person-to-person variability in the ability to process salt.

03

Control and Uncontrollable Factors

Determine whether each identified factor can be controlled in the study: 1. Salt consumption - This can be controlled by setting a specific daily salt intake for participants.2. Consumption of fruits and vegetables - This can be controlled by adjusting the participants' diet to include a specific amount of fruits and vegetables. 3. Person-to-person variability in the ability to process salt - This cannot be controlled because no method exists for identifying individuals with higher salt-processing capability. To reduce variability, researchers should ensure a large, diverse participant group.

04

Recommend Number of Treatments

To determine the number of treatments, consider all combinations of controllable factors. Create groups based on different levels of salt intake and fruits and vegetables consumption. For example, if you have two levels of salt (low and high) and two levels of fruits and vegetables (low and high), you will have 2 x 2 = 4 treatment groups. Therefore, recommend 4 treatments.

Unlock Step-by-Step Solutions & Ace Your Exams!

• Full Textbook Solutions

  Get detailed explanations and key concepts

• Unlimited Al creation

  Al flashcards, explanations, exams and more...

• Ads-free access

  To over 500 millions flashcards

• Money-back guarantee

  We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Response Variable

Understanding the response variable is crucial in any experiment. It is essentially what the researchers are measuring or observing. In this exercise, the response variable is the incidence of hypertension (high blood pressure). This means that the researchers are interested in seeing how different levels of salt consumption and other factors affect the participants' blood pressure levels.
By identifying this variable, researchers can focus on collecting relevant data related to hypertension. This helps in simplifying data analysis and drawing accurate conclusions.

Factors in Experiments

Factors are the variables that researchers manipulate or measure to see their effect on the response variable. In this experiment, three primary factors have been identified:

• Salt Consumption: The amount of salt consumed by the participants.
  
• Consumption of Fruits and Vegetables: The quantity of fruits and vegetables included in the participants' diet.
  
• Person-to-Person Variability: The natural differences in each individual's ability to process salt due to genetic or other biological factors.
  

Understanding these factors helps in designing the experiment and ensuring that all potential influencers of the response variable are considered.

Controllable and Uncontrollable Variables

Not all factors in an experiment can be controlled. Here, we explore which factors can be managed and which cannot:

• Controllable Factors:
  
  • Salt Consumption: By setting specific daily salt intake levels, researchers can manage this factor.
    
  • Consumption of Fruits and Vegetables: Participants' diets can be adjusted to include a predetermined amount of fruits and vegetables.
    


• Uncontrollable Factors:
  
  • Person-to-Person Variability: Natural differences in salt processing can't be controlled because there's no current method to identify individuals with higher salt processing abilities. To minimize variability, a large and diverse participant group should be used, spreading out the natural differences across the population.
    

Classifying factors into controllable and uncontrollable helps in reducing bias and variability, which enhances the accuracy of the experiment.

Treatment Groups

Treatment groups are formed based on the combinations of different levels of controllable factors. For this study, the following strategy can be used:
If there are two levels of salt intake (low, high) and two levels of fruits and vegetables consumption (low, high), you would create four distinct groups. This is because:

Number of treatments = Levels of Factor 1 (Salt) x Levels of Factor 2 (Fruits and Vegetables) = 2 x 2 = 4 treatment groups.
Forming these groups helps in isolating the effects of each factor combination on the response variable. Properly structured treatment groups ensure that the experiment can pinpoint which specific combinations of factors are most influential in affecting blood pressure.