Question 1

Random assignment is feasible only when an investigator is using a manipulative experimental strategy to "create" values on an independent variable.

Accepted Answer

Random assignment involves randomly assigning participants to different levels of an independent variable in order to control for extraneous variables. This is typically done in manipulative experimental designs where the researcher is actively manipulating the independent variable to observe its effect on the dependent variable. Without a manipulative experimental design, there may not be an independent variable to manipulate and therefore random assignment would not be relevant.

Question 2

Since experimental independent variables will always be confounded with all other variables that are naturally related to them,causal inferences are typically not possible when an experimental research strategy is used.

Accepted Answer

While there is always the possibility of confounding variables in any research design, experimental research allows for greater control over extraneous variables and can increase the possibility of making causal inferences.

Question 3

A confounding variable is one that is related to the independent variable (the presumed cause)and that affects the dependent variable (the presumed effect),rendering a relational inference between the independent variable and the dependent variable ambiguous.

Accepted Answer

This is the correct definition of a confounding variable. It can create ambiguity in the relationship between the independent and dependent variables.

Question 4

When an experimental research strategy is used,inferences of causation can be made only when confounded variables are controlled.

Accepted Answer

This is true because experimental research involves manipulating an independent variable and measuring the effect on a dependent variable. To make inferences about causation, it is necessary to control for any other variables that could influence the outcome (confounding variables). This is often achieved through random assignment to treatment groups and/or using control groups.

Question 5

In practice,it is often difficult to identify appropriate variables to serve as a basis
for matching,and,once identified,to readily complete the matching process.

Accepted Answer

Identifying appropriate variables for matching can be challenging and time-consuming, and even if suitable variables are found, the matching process itself may still be difficult to complete accurately.

Question 6

Random assignment guarantees that the research groups will not differ beforehand on the dependent variable.

Accepted Answer

Random assignment aims to equalize groups on all variables, both known and unknown, to isolate the effect of the independent variable. However, it does not guarantee that groups will not differ at all on the dependent variable or other characteristics due to chance.

Question 7

Between-subjects designs and within-subjects designs are both viable strategies only when the independent variable is experimental in nature.

Accepted Answer

While both between-subjects and within-subjects designs are common in experimental research, the independent variable does not necessarily have to be experimental in nature. For example, a study measuring the relationship between personality traits and job satisfaction could use either design type.

Question 8

A between-subjects variable is one whose values are "split up" between subjects instead of occurring completely within the same individuals.

Accepted Answer

A between-subjects variable refers to a variable that is different between different individuals or groups of participants in a study, i.e. it is split up between the subjects. A within-subjects variable, on the other hand, has values that occur within the same individuals.

Question 9

A procedure for reducing sampling error is to define the groups such that the variances of scores in the populations (ó²)will be smaller.

Accepted Answer

When the variances of scores in the populations are smaller, it means that there is less variability within each group. This can lead to more representative samples and less sampling error. Therefore, defining groups with smaller variances can help reduce sampling error.

Question 10

Since random assignment cannot be applied to experimental groups,experimental
variables will always be confounded with all other variables that are naturally related to them.

Accepted Answer

Random assignment can be applied to experimental groups, and it is actually recommended to do so in order to minimize the confounding of variables. Random assignment helps to ensure that the different groups being compared are as similar as possible at the beginning of the study, which increases the chances that any differences observed between them can be attributed to the independent variable being manipulated.

Question 11

One advantage of the between-subjects approach as compared with the within-subjects approach is that it is more economical in terms of the number of research participants.

Accepted Answer

The answer of One advantage of the between-subjects approach as...

Question 12

Random assignment is an effective method for controlling confounding variables defined by individual differences.

Accepted Answer

Random assignment helps control confounding variables by ensuring that participants are distributed equally among different experimental groups, minimizing the impact of individual differences on the results.

Question 13

One way an investigator can reduce sampling error is to reduce the sample sizes for the various groups.

Accepted Answer

In order to reduce sampling error, the investigator should strive to increase sample sizes for the various groups rather than reduce them. Larger sample sizes lead to more accurate and representative results.

Question 14

A disturbance variable is one that is related to the independent variable (and hence,confounded with it)but that also affects the dependent variable.

Accepted Answer

The answer of A disturbance variable is one that is...

Question 15

It is entirely possible for two variables to be related to one another,but for no causal relationship to exist between them.

Accepted Answer

Just because two variables are correlated or associated with each other does not mean that one variable causes the other. There may be other factors or variables that are causing both variables to change in a similar way. This is why it is important to establish causal relationships through research studies with experimental designs.

Question 16

The ability to make a causal inference between two variables is a function of the statistical techniques one uses,not the research design used to generate the data that are analyzed by those statistical techniques.

Accepted Answer

The ability to make a causal inference between two variables is determined by both the statistical techniques used and the research design that was used to collect the data. The research design must incorporate features such as random assignment or natural experiments to establish a cause-and-effect relationship between the variables. Simply using sophisticated statistical techniques on observational data cannot establish causality.

Question 17

The major disadvantage of holding a variable constant is that it may restrict the generalizability of the results.

Accepted Answer

When a variable is held constant, it may not accurately reflect real-world scenarios, which can limit the applicability of the results to a broader population or setting.

Question 18

For many observational independent variables,only between-subjects designs are applicable.

Accepted Answer

Observational independent variables refer to variables that cannot be manipulated by the researcher, such as age, gender, and race. In some cases, it may be possible to use within-subjects designs to study these variables (e.g., by measuring changes over time within the same individuals). However, for many observational independent variables, only between-subjects designs are applicable.

Question 19

With the technique of matching,an individual in one group is "matched" with an individual in each of the other groups such that all of these individuals have the
same value on the independent variable.

Accepted Answer

In matching, individuals in different groups are matched based on similar values of one or more variables, not necessarily the independent variable. The purpose is to control for those variables, not to have identical values on the independent variable.

Question 20

A disturbance variable increases sampling error by increasing variability within groups.

Accepted Answer

A disturbance variable can introduce additional sources of variability within groups, which can lead to an increase in sampling error. This is because the disturbance variable can make it more difficult to determine whether observed differences between group means are due to the treatment or the disturbance variable.

Quiz 9: Principles of Research Design and Statistical Preliminaries for Analyzing Bivariate Relationships