Question

A researcher studied a group of identical twins who had been separated and adopted at birth. In each case, one twin (Twin A) was adopted by a low-income family and the other (Twin B) by a high-income family. Both twins were given an IQ test as adults. Here are their scores:

$100$ IQ and twins (3.1) How well does one twin’s IQ predict the other’s? Give appropriate evidence to support your answer.

Short answer

In the residual plot, Twin A is on the horizontal axis and the residual is on the vertical axis. Because there is no discernible trend in the scatterplot, the linear regression line looks to make reasonable predictions for Twin B's IQ scores.

Step-by-step solution

Given information

Twin A:	120	99	99	94	111	97	99	94	104	114	113	100
Twin B:	128	104	108	100	116	105	100	100	103	124	114	112

Concept

The treatments are randomly assigned to all of the experimental units in a completely randomized design.

In a double-blind experiment, neither the subjects nor the persons who interact with them and evaluate their responses are aware of the therapy they received.

Observational research looks at people and assesses factors of interest without trying to affect their responses.

Individuals are purposely subjected to a treatment in order to measure their responses in an experiment.

Explanation

A researcher analyzed a group of identical twins who had been separated and adopted at birth, according to the query. As a result, using the information provided in the question, create the following scatterplot:

Twin A is on the horizontal axis and Twin B is on the vertical axis in this scatterplot. Because the scatterplot slopes upward, the variables have a positive relationship. Furthermore, the spots appear to be about centered on a line, indicating that the link is linear. Let's make a residual plot of the linear regression line now. A residual is a difference between the actual value and the linear regression line's anticipated value. As a result, it is as follows: Twin A is on the horizontal axis, while the residual is on the vertical axis, in the residual plot. Because the scatterplot shows no evident trend, the linear regression line appears to make fair predictions for Twin B's IQ values.