CHAPTER 8 Reversion to the Mean Flashcards
What is reversion to the mean?
A phenomenon where extreme observations are often followed by less extreme observations.
What outcomes tend to exhibit reversion to the mean?
Any outcome that is a function of both signal and noise.
Why is it important to understand reversion to the mean?
To avoid misinterpreting evidence and quantitative information.
Should we expect reversion to the mean for future projections like stock prices?
No, we shouldn’t expect reversion to the mean for beliefs about the future.
What is the replication crisis?
The failure to replicate hyped scientific results in follow-up studies.
Who is Jonathan Schooler?
A psychologist who noticed systematic failures to replicate findings in his studies.
What happens to the effect sizes in replicated studies according to Schooler’s observations?
Effects tend to get systematically smaller.
What is the Hawthorne effect?
When subjects change their behavior because they know they are being studied.
What are demand effects?
Situations where subjects behave differently to please the experimenters.
What is cosmic habituation as proposed by Schooler?
The idea that the universe causes effects to shrink every time they are studied.
What did Francis Galton study in the 1860s?
The relationship between the size of parents and their children, particularly in height.
What does Galton’s regression line indicate about parents’ and children’s heights?
Taller parents tend to have taller children, but the slope is less than 1.
What is the positive y-intercept in Galton’s regression line suggest?
Particularly short parents tend to have children who are taller than they are.
What is regression to mediocrity?
A phenomenon where extreme measurements tend to revert toward the mean.
How does Galton’s findings relate to cosmic habituation?
Both suggest some unseen force pushes outcomes toward the average.
What are the two main factors influencing seed size according to the model?
- Genes inherited from the parent
- Amount of sunlight received while growing
What happens to exceptionally large or small seeds when they produce offspring?
Their offspring will tend to be larger than average but smaller than their parents.
What is the relationship between signal and noise in the context of reversion to the mean?
Reversion to the mean occurs in outcomes that are partly systematic (signal) and partly random (noise).
What is a common misconception about reversion to the mean?
That it reflects a gravitational pull toward the mean.
In the example with John Junior and John III, what is the expected height of John III?
Shorter than John Junior.
For John Junior’s father, what is the expected height compared to John Junior?
Shorter than John Junior.
Why might people confuse the expected heights of John Junior and his father?
They might reason that reversion to the mean implies John Senior must be much taller.
What is the key takeaway regarding reversion to the mean?
It is crucial for interpreting evidence correctly across various contexts.
What is reversion to the mean?
A statistical phenomenon where extreme observations tend to be followed by more moderate ones
If John Junior is very tall, what can we expect about his father’s height?
His father is probably shorter than him due to reversion to the mean
What is the relationship between the signal and noise in observations?
An outcome is made up of a signal (true value) and noise (random variation)
True or False: Reversion to the mean is a gravitational force pulling things toward the average over time.
False
What do we generally observe about scores in athletic competitions over time?
Scores tend to revert to the mean, showing a pattern of improvement or decline
In the context of golf scores, what does a shallower regression line indicate?
Players who perform above average in one round tend to perform worse in the next round
Fill in the blank: Golf scores are a function of both skill (signal) and _______.
[noise]
What might explain why a player who had a good score in round 2 had a worse score in round 1?
Reversion to the mean, not necessarily pressure from performing well
What is the implication of seeking help when performance is unexpectedly poor?
It may lead to misattributing improvement to the help received rather than reversion to the mean
Why might people believe that chiropractic adjustments or test prep strategies are effective?
Because people often seek help when at their worst, leading to natural improvement
What is a common misconception about broken-windows policing?
That it is effective, while reversion to the mean may explain the observed decrease in crime
What did a 2002 study on arthroscopic knee surgery reveal?
The surgery had no detectable effect on knee pain compared to sham surgery
True or False: The placebo effect is when belief in treatment activates the body’s healing powers.
True
What do medical researchers use to account for the placebo effect in trials?
Control groups receiving placebos, like sugar pills or fake surgeries
What is one consequence of failing to consider reversion to the mean in scientific studies?
It can lead to misinterpretation of the effectiveness of interventions
What is the placebo effect?
The phenomenon where believing you’re receiving a treatment can lead to health improvements, even without actual treatment.
Placebos can include sugar pills or fake surgeries.
What is a treatment group in medical trials?
The group that receives the actual drug or treatment being tested.
What is a control group in medical trials?
The group that receives a placebo treatment for comparison against the treatment group.
Why is the improvement of the control group seen as evidence for the placebo effect?
Because both the treatment and control groups often show health improvements.
What is reversion to the mean?
The statistical phenomenon where extreme observations tend to be followed by more average ones.
What is a more effective way to test for a placebo effect?
Dividing the subjects into a group that receives a placebo and a group that receives no treatment at all.
What did the 2011 study by Harvard Medical School find regarding asthma treatments?
Only the real treatment improved lung capacity, while placebo treatments did not.
What is the implication of the findings regarding the placebo effect?
It suggests that the placebo effect may reflect mind over mind, not mind over matter.
Who is Linus Pauling and what is his relation to vitamin C?
A chemist who advocated for vitamin C’s health benefits, despite little evidence supporting its effectiveness beyond preventing scurvy.
What are the components of an estimate from data according to the favorite equation?
The true estimand, bias, and noise.
What causes estimates to vary across different studies of the same phenomenon?
Noise from sampling variation.
What is cosmic habituation?
The phenomenon where estimated effects tend to decrease in magnitude upon replication due to reversion to the mean.
What role does publication bias play in scientific studies?
It affects which studies are published and replicated, often favoring surprising or statistically significant findings.
What is the efficient-market hypothesis?
The theory that stock prices reflect all available information and that it is impossible to consistently predict price changes.
In which scenarios should we not expect reversion to the mean?
When the signal is much greater than the noise.
Why is there typically no reversion to the mean in stock prices?
Because stock prices reflect investors’ beliefs about the future, not just past performance.
True or False: Beliefs can revert to the mean.
False.
What are some challenges created by the presence of noise in data?
Over-comparing, under-reporting, and reversion to the mean.
What is bias in the context of estimating relationships?
A systematic error that can affect the accuracy of estimates, particularly in causal relationships.
What is the Hawthorne effect?
The phenomenon whereby subjects change their behavior because they know they are being studied.
What is a demand effect?
A specific instance of a Hawthorne effect in which research subjects change their behavior to try to please the researcher.
Define signal in the context of outcomes.
The systematic component of an outcome that is persistent across observations.
Define noise in the context of outcomes.
Random components of an outcome that change from observation to observation.
What is reversion to the mean?
The phenomenon whereby, if one observation of an outcome made up of signal and noise is particularly large (respectively, small), other observations will typically be smaller (respectively, larger).
True or False: Bias is a concern when learning about causal relationships.
True.
What does the phrase ‘correlation doesn’t imply causation’ mean?
The correlation between two features of the world may be a biased estimate of the causal relationship between them.
What is the Dunning-Kruger effect?
The phenomenon where people with low ability in a domain overestimate their ability, while those with high ability are more accurate in assessing their own skills.
What is the typical evidence for the Dunning-Kruger hypothesis?
Subjects tend to overestimate their IQ when they have low IQs and are more accurate when they have high IQs.
Fill in the blank: The systematic component of an outcome is known as _______.
[signal]
Fill in the blank: Random components of an outcome that change from observation to observation are known as _______.
[noise]
What might you want to analyze to understand if players lose their nerve when aiming to break a record?
Collect data on performance under pressure and analyze trends in performance over time.
What happens to a player’s performance after an exceptional start to a season, according to the concept of reversion to the mean?
They are likely to hit fewer home runs than in the initial exceptional games.
What is the implication of mean reversion in stock prices?
It suggests that after a significant drop, a stock may not necessarily rebound as expected.
In the context of self-assessment, what is the relationship between ability and accurate assessment according to psychologists?
A person’s ability in a domain affects their capacity to accurately assess their own ability.
What is one potential flaw in the reasoning that if Paul’s son has a genius-level IQ, Paul must have a super-genius-level IQ?
Mean reversion; it does not necessarily follow that Paul’s IQ is higher due to John’s exceptional score.
What should you consider when analyzing claims about phenomena that could be explained by mean reversion?
Evaluate the evidence presented and explore alternative explanations that account for the data.
What is a common misconception related to the Hawthorne effect?
That changes in behavior are solely due to awareness of being studied, when they may be caused by other factors.
What is the focus of Part 3 in the discussed content?
Examining the sources of bias in causal relationships and strategies for estimating them in an unbiased way.
What is the significance of the figure showing the relationship between self-assessed IQ and test-assessed IQ?
It illustrates that people with low IQs tend to overestimate their abilities, while those with high IQs are more accurate.
What did Levitt and List (2011) analyze regarding the Hawthorne effect?
They showed that the original data suggesting a Hawthorne effect was likely misinterpreted and attributed to other factors.
