With the aid of examples briefly explain the difference between fixed effect and random effects models in experimental design.

Study design
asked 2021-02-16
With the aid of examples briefly explain the difference between fixed effect and random effects models in experimental design.

Answers (1)

Step 1
Experimental study:
In a designed experimental study, researchers allocate individuals to a certain group under study and change the values of an explanatory variable intentionally, after which, the values of the response variable for each group is recorded.
Step 2
Fixed effect:
The fixed effect in an experimental design is defined as the data that has been gathered from all the levels of the factor that are of interest. Fixed effects will be constant across the individuals.
Suppose that 3 different dosages of drug are given to three different groups of subjects. The objective of the investigator is to compare the effect of reactions of three different dosages of a drug. In the given scenario "Dosage" is the factor and 3 different dosages of drug are 3 different levels of the experiment. Here, interaction of any 2 dosages is not included in the experiment. That is, the investigator is studying only fixed effect. Main interest is effect of each dosage.
Random effect:
The random effect in an experimental design is defined as the factor that have many possible levels, interest is in all possible levels, but only a random sample of levels is included in the data. The random effect is constant across individuals.
Suppose that patients are classified into 2 surgical procedures randomly and there are five separate surgical teams. To prevent potential conflict between care and surgical team, each team is qualified in both procedures, and each team performs equal numbers in each in the two types of operations. As the investigator wants to compare the procedures, the goal is to generalize to other surgical teams. The surgical team is a random factor, not a fixed factor.

Relevant Questions

asked 2020-12-30
Is the gift you purchased for that special someone really appreciated? This was the question investigated in the Journal of Experimental Social Psychology (Vol. 45, 2009). Toe researchers examined the link between engagement ring price (dollars) and level of appreciation of the recipient \(\displaystyle{\left(\text{measured on a 7-point scale where}\ {1}=\ \text{"not at all" and}\ {7}=\ \text{to a great extent"}\right)}.\) Participants for the study were those who used a popular Web site for engaged couples. The Web site's directory was searched for those with "average" American names (e.g., "John Smith," "Sara Jones"). These individuals were then invited to participate in an online survey in exchange for a $10 gift certificate. Of the respondents, those who paid really high or really low prices for the ring were excluded, leaving a sample size of 33 respondents. a) Identify the experimental units for this study. b) What are the variables of interest? Are they quantitative or qualitative in nature? c) Describe the population of interest. d) Do you believe the sample of 33 respondents is representative of the population? Explain. e. In a second, designed study, the researchers investigated whether the link between gift price and level of appreciation was stronger for birthday gift givers than for birthday gift receivers. Toe participants were randomly assigned to play the role of gift-giver or gift-receiver. Assume that the sample consists of 50 individuals. Use a random number generator to randomly assign 25 individuals to play the gift-receiver role and 25 to play the gift-giver role.
asked 2020-11-08
A researcher is conducting a study to examine the effects of cognitive behavior therapy for the treatment of social anxiety in a sample of 16 participants. He measures the social anxiety scores of participants before the tratment and then again after treatment and the resulting data is as follows:
n=16, M_0=5, s =4
a) What type of design is this study (single-sample, independent measures, repeated measures)
b)State the null and alternate hypotheses
c) Using an \(\displaystyle\alpha\le{v}{e}{l}{o}{f}{.05}{\left(\alpha={.05}\right)}\), identify the critical values of t for a 2-tailed test.
asked 2021-02-16
Participants enter a research study with unique characteristics that produce different scores from one person to another. For an independent-measures study, these individual differences can cause problems. Identify the problems and briefly explain how they are eliminated or reduced with a repeated-measures study. Independent-measures study is used in the study.
asked 2020-11-09
What is the difference between a between-subjects design and a within-subject design? Which t-test is used for each design? Provide a real- life example of a between-subjects design and a within-subjects design.
asked 2020-10-27
To find:The conditions for the population and the study design that are required by the procedure and are used to contruct the confidence interval.
To identify:The important conditions for the validity of the procedure in the given case.
In an experiment on the effect of calcium and blood pressure, 54 healthy white males are divided into two groups’ calcium and placebo. The summary statistic for the systolic blood pressure of the 27 members of the placebo group is ¥ = 114.9 and s=9.3.
asked 2020-12-28
Explain what is wrong with the study design.
In a study to determine the factors that are associated with strong academic performance. 20 students are considered who are having perfect GPAs of 4.0. The explanatory variables like high school GPA and average amount of time spent studying per day are measured.
asked 2021-02-19
Is wrapping a banana in plastic wrap and leaving the other bananas alone to see which one rots faster and experimental study design or and observational study design?
asked 2020-10-27
Identify the type of random sampling used in the study design.
The researcher is interested compare the student's loan debt for the students who attend four-year public universities and four-year private universities. A random sample of 100 graduates of the public universities and 100 graduates of private universities are taken.
asked 2021-02-09
Know these terms. Explain in one sentence each what “randomized,” “double-blind,” and “placebo-controlled” mean in the description of the design of the study.
Experiment basics. Identify the subjects, the explanatory variable, and several response variables for this study.
asked 2021-03-09
A proposed study design is to leave 100 questionnaires by the checkout line in a student cafeteria. The questionnaire can be picked up by any student and returned to the cashier. Explain why this volunteer sample is a poor study design.