Question

2\. DRAWING CONCLUSIONS A researcher wants to test the effectiveness of reading novels on raising intelligence quotient (IQ) scores. Identify a potential problem, if any, with each experimental design. Then describe how you can improve it. a. The researcher selects 500 adults and randomly divides them into two groups. One group reads novels daily and one group does not read novels. At the end of 1 year, each adult is evaluated and it is determined that neither group had an increase in IQ scores. b. Fifty adults volunteer to spend time reading novels every day for 1 year. Fifty other adults volunteer to refrain from reading novels for 1 year. Each adult is evaluated and it is determined that the adults who read novels raised their IQ scores by 3 points more than the other group

Short answer

The potential problem for experiment A is that it has confounding variables and lacks an appropriate control activity. It can be improved by introducing a control task that's similar to reading. In experiment B, the issue lies in self-selection bias due to voluntary participation. The study would be improved by randomly assigning individuals to each group.

Step-by-step solution

Analyze experiment design for Part A

In the case of experiment A, a potential problem that can arise is the lack of control of confounding variables. Factors like participant's daily activities, mental state, general reading habits, etc. can influence their IQ scores. Since the control group is not engaged in a specifically similar activity to reading, it's also uncertain if the lack of an effect is due to the intervention (reading novels) or the lack of an equivalent control task. Hence, the experiment lacks internal validity.

Improve experiment design for Part A

An improved design would include a control task for the other group that's intellectually stimulating but not reading novels, for example solving puzzles. This ensures a more equal standing ground for both intervention groups, making them more comparable.

Analyze experiment design for Part B

In the case of experiment B, volunteers were used for the study. The issue arises here in the voluntariness; it leads to self-selection bias. That is, individuals who are willing to voluntarily participate in such studies might already be more inclined to read, hence more likely to show an increased IQ.

Improve experiment design for Part B

A suggestion for an improved design would be to randomly assign individuals to either group, rather than allowing them to volunteer for a particular one. This way, the collected data would be less likely to skew based on participant's personal inclinations.

Key concepts

Control Group

In an experiment, a control group is a crucial component needed to accurately measure the effects of an intervention. Think of it as a baseline group that does not receive the experimental treatment, helping to illuminate what changes occur due to the experiment itself. Without a control group, it becomes difficult to determine whether any change happened directly because of the intervention or was a natural fluctuation.

Consider an experiment examining the impact of reading novels on IQ scores. If you have a group reading novels but no control group, you may assume any IQ change is due to novel reading. However, other factors like natural cognitive growth, lifestyle changes, or uncontrollable variables could be the actual cause of any observed changes. This makes results unreliable.

A strong control group should:

• Not receive the treatment but partake in an activity similar in engagement.
• Be structurally identical to the experimental group aside from the treatment.

This way, any difference in outcomes between groups can more confidently be attributed to the intervention.

Confounding Variables

Confounding variables are like hidden culprits in research that can skew the results or alter the outcomes of an experiment. These are outside influences that might change the effect of the treatment, different from the key variable being tested.

In the context of the novel reading study, potential confounding variables might be participants' education level, their initial interest in reading, or varying daily intellectual activities. Such factors can lead to false conclusions if not properly accounted for.

To handle confounding variables effectively, researchers must:

• Identify potential confounders before starting the experiment.
• Keep conditions as consistent as possible across groups.
• Use controlled tasks or randomization to average out these influences.

By reducing the impact of these variables, the results are more likely to reveal the true effect of the novel reading intervention.

Self-selection Bias

Self-selection bias occurs when participants, rather than researchers, decide which group they belong to in an experiment. This bias happens because individuals who opt-in for a study may share characteristics influencing the study's outcome.

In the case of the novel reading experiment, if participants choose whether to read or not, those who pick the reading group might already enjoy reading or likely engage in activities that enhance cognitive skills. This leads to biased results, as the observed difference might be due to preexisting traits rather than the reading itself.

To prevent self-selection bias:

• Use random assignment to assign participants to groups, rather than allowing them to choose.
• Ensure pre-test screenings or background checks to balance group characteristics.

Taking these steps helps ensure any observed changes genuinely result from the experimental conditions rather than inherent participant differences.

Random Assignment

Random assignment is a meticulous process central to a robust experimental design that significantly boosts the validity of a study. It involves allocating participants to different groups purely by chance, minimizing biases and distributing characteristics evenly across all groups.

Returning to the novel reading experiment, random assignment ensures that every participant has an equal chance of being placed in either the reading or non-reading group. This method reduces the likelihood of confounding variables or biases distorting the results.

The benefits of random assignment include:

• Ensuring each group is equivalent at the start of the experiment.
• Reducing systematic differences between groups.
• Increasing the reliability and validity of the study findings.

By implementing random assignment, researchers can more accurately attribute any observed changes in IQ to the intervention—reading novels—rather than pre-existing differences among participants.