Dr. Sparrow is a social psychologist who studies romantic relationships. Several researchers have found that there is a link between income and marital satisfaction (e.g., Dakin & Wampler, 2008). Dr. Sparrow is curious as to whether there is a causal link between the two variables, such that having a higher income causes higher levels of marital satisfaction. He is confident that he cannot reasonably or ethically manipulate people's income level, so he decides to use a multivariate design. He is also curious as to whether there is a causal link between these two variables or if two other variables (number of arguments and life satisfaction) can explain the relationship. He measures his three variables in a sample of 124 married couples recruited from a local community center. Below are his results.
DV: Marital Satisfaction
Variable Beta (b) Significance ( p)
Income
.69
.03
Number of arguments
-.73
.01
Life satisfaction
.13
.81
Refer to Research Study 9.2 to answer the following four questions.
Given Dr. Sparrow's design, which of the following problems is his study best able to overcome?