Read the responses and see what's a possible third variable (that has not already been proposed) that could explain the relationship between the two target variables.

Researchers are interested in understanding the potential relationship between children's IQ and their sibling status, as measured by whether they are only children or have siblings. The researchers give children an IQ test (the WISC-V, a standard test for assessing children's IQ) and ask about how many siblings they have. All children are then coded as having 0 siblings or having siblings.

1) Restate the two variables here: Do the children have siblings or not and the IQ of the children

2) Are the variables quantitative or categorical? The variable IQ is Quantitative, and the variable for the number of siblings is categorical.

3) Are the variables measured or manipulated? The variable IQ is measured,and the variable number of siblings is manipulated.

4) Which should the researchers use to analyze their data, a t-test, or a correlation coefficient?

A t-test

5) Is the design of this study correlational or experimental? Justify your answer.

Correlational the point of the experiment is to see if there is a correlation between a child's IQ and the number of siblings they have.

ONCE YOU HAVE COMPLETED PARTS 1-5, you can move on to part 6. Part 6 adds some new information, which you should not consider when you're answering parts 1-5.

6) Findings: Let's suppose the researchers find that only children have higher IQs than children with siblings. Now, consider whether, given this information, you have grounds for a claim of causationparticularly for the claim that being an only child leads to higher IQs.

A claim for causation could be that as an only child, parents have more time to spend with that child doing activities that could help them learn.

6a) Is there covariance? Explain what that means, and how you know there is or is not covariance.

Yes.Covariance is a formula that can be used to measure the variation between two variables and see if there is a positive or negative relationship between them. Because the data showed that only children have a higher IQ than children with siblings, there is covariance.

6b) Is there temporal precedence? Explain what that means, and how you know that there is or is not temporal precedence.

Temporal precedence is manipulating the hypothesized cause and measuring the effect on the outcomes.Because the IQ test was given first, there is no temporal precedence. If the children were asked how many siblings, they have first, there would be a temporal precedence.

6c) Is there an internal validity problem? That is, is there a third variable that might be causing both other variables? No there is no internal validity problem.

7a) Finally, let's suppose that all the participants in this study were males. What would you think about the external validity of this study? To whom might these results generalize, and to whom may they not generalize?The results would generalize to boys and not to girls.

7b) Consider the possibility that gender may moderate the relationship between IQ and sibling status. What would that mean? Propose one pattern of results that would show this relationship (multiple patterns could occur!).

It would mean that gender is added as a third variable in the study. A pattern that would show this relationship is that boys without siblings had higher IQs than girls without siblings