Showing posts with label Experiment. Show all posts
Showing posts with label Experiment. Show all posts

Monday, May 20, 2013

An In Depth Look at a Mindfulness and Stress Study

My former classmate at the University of Hartford, Tonya Jacobs, had an article described in the Huffington Post titled Mindfulness Meditation Could Lower Levels Of Cortisol, The Stress Hormone.  It described her study which originally appeared in the Journal of Health Psychology.  It talks about how a study was conducted of those who participated in a three month meditation retreat where it says mindfulness was measured along with cortisol levels in saliva as a measure of stress.  If found that cortisol (a hormone that strongly indicates stress) levels were decreased from the beginning of the retreat to the end as mindfulness increased.  They warned that there was no control group.

From past experience I know that the news media often leaves out important details of a study and can be bad at interpreting the results of the studies.  I thought I would take a look Jacobs et al. (2013) original article which has a lot more detail to allow one to replicate the study.  In the methods sections they state that there was a treatment group of 30 for those who participated in the retreat and a control group of 30 who were wait listed for the retreat using stratified random sampling to control for any potential confounding variables such as BMI (Body Mass Index which is weight divided by height squared and is a crude measure of obesity), handedness and IQ.  The wait listed group did receive the mindfulness intervention after the treatment group.  

The authors do not discuss if there is a difference between the wait list and non waitlist groups in cortisol or mindfulness levels especially during the time where the wait list group was not receiving the intervention.  This may not have been feasible during the study as the individuals were probably scattered all over the US and measurements of cortisol and mindfulness could not be taken without great cost.  Participants were paid during the retreat.  Three participants had incomplete data and were excluded from the data analysis.  

The results showed no overall effect of cortisol decrease from pre to post measurements but did significantly decrease for BMI.  Mindfulness significantly increased between the pre and post.  The pre and post cortisol levels were significantly negatively correlated with mindfulness as measured by a 37 item questionnaire which was previously validated.  Negatively correlated means that as mindfulness increases cortisol levels decrease.  This effect was still significant after adjusting for age and BMI.

The authors acknowledge that this study is correlational and does not establish a cause and effect relationship between meditation, mindfulness, and stress.  The article in the Huffington Post seems to suggest the same thing by stating that there is no control group.  Because of the difficulty in doing this type of research, the need for more of theses types of studies is established.  Experimental studies with a well defined control and treatment group with all other confounding variables are adjusted for are ideal for establishing cause and effect relationships.  The ideal of research is seldom met.  When the situation is less than ideal, converging validation with many different methods is needed to accomplish the same cause-effect relationship.  

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Draft Logic

Sunday, April 29, 2012

Draft Logic

ESPN & the NFL Network have come out with blanket coverage of the National Football League draft which is the largest gym class method of picking teams (I was never picked first even for dodge ball).  A lot of intelligence is expended on these picks as can be seen in this famous exchange between ESPN's Mel Kiper (in the clip above from 1994) and the Indianapolis Colts Bill Tobin (seen below, introduced by a mustached Keith Olbermann). Two years later the Colts almost made it to the Super Bowl.

The logic of the draft is simple. The team with the worst record (the Colts this year) from the last season gets to choose first from the top players coming out of college while the team with the second worst record picks second and goes down the line until it gets to the Super Bowl Champion who picks last in the round.  The picks are a reflection of which players are available and what the team's needs (or what the teams believe that their needs) are.  The exchange above shows how passionate people's beliefs about a teams needs can be. Steeler's coach Chuck Noll was called a genius for his drafting in the 1970s which built their dynasty in that decade.  Later he was heavily criticized for passing on Dan Marino in 1983 (although almost every other team did too except Miami which picked next to last that year). Imagine what problems could be solved if all that energy and talent were trained on the real problems of the world such as cancer and global warming.

This method of picking players for pro sports teams works well in evening out the talent among the teams, along with the salary cap.  This kind of purposeful selection does not work for surveys, polls, and clinical trials because the selections made are a reflection of the selectors biases.  Such a survey was done in the 1948 Presidential Election where pollsters selected individuals to meet a quota for gender and other variable in order to make the sample representative according to the variables that they thought were important and the picture at the left was the result.  Random sampling has been used since 1948 because it is unbiased with respect to all of the other that are not accounted for by the researchers or coaches.  Random sampling may not work for the NFL or other pro sports leagues but high school/junior high gym classes could benefit from randomly assigning kids to teams and having them work together. That would encourage kids to cooperate more.

An example of a Monte Carlo experiment would be to have a group of fans pick their fantasy league teams using the draft method and then have a computer select the league by random using a computer and compare how their respective teams perform over the season.  Some teams may differ but overall they will be similar.

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Sunday, July 10, 2011

Casey Anthony's "CSI" Effect

The shock waves still continue to emanate from the Casey Anthony trial where the young Florida mother was acquitted of murdering her 3 year old daughter but convicted of the lesser offenses of lying to police.  Rendering a verdict in court cases is much like testing hypotheses in statistics.  The researcher (or the jury) makes a decision based on the data (aka evidence) that is available and based on the likelihood of this data (or evidence) being observed when the research hypothesis is assumed false (ie. presumed innocent until proven guilty).  This decision is later compared to some objective truth (which if you're religious only God and maybe the perpetrator would know for certain). Criminal trials are seldom as clear on guilt or innocence as that of Richard Poplawski.  There are two types of errors that can be made: the first is to put an innocent person in prison and the second is to let a guilty person go free.  The founding fathers considered the first error to be the more serious as Ms. Anthony can now never be tried again for this crime.
Criminologists have talked about a CSI effect where juries expect police and prosecutors to have detailed physical evidence tying the accused to the crime scene and the victim.  This may or may not have happened in this case, I haven't followed it that closely.  Of course in scientific research, the news media and the public is often far less critical of published research findings often latching on to them (especially when it supports what one already believes) unquestioningly.  In both of these cases one's emotions can override one's rational faculties when things like the death of a child are involved.

Jack the Ripper was never caught in the Victorian era at least partly because CSI tools like finger printing or DNA analysis were not available in the 19th century.  Arthur Conan Doyle started writing the Sherlock Holmes novels and short stories about the same time as Jack was active.  It may be a coincidence that Doyle's success with Holmes and the public's fear and frustration with Jack the Ripper but I doubt it.  Just as modern police hate shows like CSI I wonder what real Victorian detectives thought of Doyle's Holmes?  My hypothesis is that they sympathized with Dr. Watson.  Look for Holmes solving the Casley Anthony case soon on CSI.
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Friday, March 18, 2011

ADHD, Genetics, and Causality: A Chicken-Egg Problem

The conventional view of Attention Deficit Hyperactivity Disorder has been to be caused by heredity, brain injury, or other birth exposures (see the CDC's fact page on ADHD for a full list and a description of the disorder).  Canadian physician Gabor Mate argues that it and a variety of other mental problems in childhood and adolescence is primarily caused by modern stressors placed on children as their brains develop. The primary thrust of his argument is given in the clip below on Democracy Now.

His view on ADHD is not the best known view which may or may not be the case in the future as prevailing views in science ebb and flow.  I asked the local director of CHADD (Children and Adults with Attention Deficit Disorder) first if she'd heard of Dr. Mate and what her reaction to his views were.  She said she was not and that her group favored the hereditary hypothesis and did not like to blame parents or society.  They prefer to build people up not tear people down.

Individuals who grew up in a chaotic household may find Dr. Mate's theories appealing.  He uses case studies and personal information from his life in his book Scattered: How ATTENTION DEFICIT DISORDER ORIGINATES and What You Can Do About It as a Jewish child in WWII Hungary and sites other studies to support his argument without going into their methodology,  A genetic link to ADHD has been established and, given this link, often parental stress can be found even in societies without these modern stressors.  Also modern societies have better tools to detect behavioral problems like ADHD which would explain the increased rate of diagnosis.  Finally as is the case on my post on autism (see Cause & Effect, Slip Slidin' Away ) it is difficult to do experiments on this disorder as it is unethical to do on people and there is no good animal model yet for ADHD.

For a more conventional explanation of the prevailing scientific view of ADHD from the documentary ADD & Loving It you can see the video in the link below.  Dr. Mate doesn't directly blame the parents but societal pressures that are put on the parents.


Where Are We in Understanding?

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Sunday, March 6, 2011

States as Laboratories and Lavatories of Democracy

As the standoff at the State Capitol in Wisconsin continues over public employees and teachers to continue to have the right to collective bargaining with no end in sight a similar bill in the Midwestern state of Ohio passed it's State Senate this week by a vote of 17-16 with protesting crowd sizes maxing out at 8,500.  According to the Dayton Daily News "The bill undoes much of the 1983 law allowing public employee collective bargaining. It bans strikes, ends binding arbitration for police and firefighters, creates a merit pay system and layoff system using criteria other than seniority."   The State House is expected to vote on the bill this week and be signed by Gov John Kasich-R (who is a former Fox News contributor).  

If one state is successful in passing this law while the other is not it will be bad for unions and workers in that state but it does present an opportunity for public policy and social science researchers to study the effects of these types of laws.  Both Wisconsin and Ohio are Midwestern industrial states of similar climate, industry, and demographic makeup.  This type of study would be called a quasi experiment (not a true experiment because the law is not randomly assigned).  A wide variety of variables could be studied as the workplace has an effect on a wide variety of quality of life issues.  The strain that public employees are under can have ripple effects throughout the state especially in times of crisis when services are needed from the State.  Even in normal times stress on the employees can have effects in their homes, on their marriages, and their kids.  If their incomes are affected so can the surrounding communities' economies. 

There is plenty of other "experimenting" going on in other states both on the left and the right.  For example Vermont is trying to pass a Single Payer law to cover everyone (see Related Post below) while Pennsylvania 42,000 adults lost health insurance due to the Adult Basic Program being ended on March 1 of this year.  In the chart on the right many states including Vermont (single payer controls costs better than private insurers) are cutting spending to below prerecession levels providing many consequences for those dependent on spending and opportunities to study the effects of these consequences.  Pennsylvania can now be added to the map in red.


Last night the Wisconsin state Senate may or may not have bended the rules and passed the law 18-1 banning collective bargaining without the quorum present.  Whether it stands or not will depend on whether court challenges to the law and/or efforts to recall Senators who voted for the law are successful.  Governor Walker can be recalled in January 2012.  This could be a different kind of experiment in democracy than what we're seeing in Ohio and other states.

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Thursday, January 6, 2011

Cause & Effect, Slip Slidin' Away

Much has been made recently of autism being linked to the measles mumps and rubella vaccine (MMR) in 1998 Lancet study being shown to be a fraud. Because of that study, a social movement led by former Playmate of the Year Jenny McCarthy who sadly had a son diagnosed with autism after being vaccinated for MMR in 2005. After hearing of this study and blaming her son's diagnosis on the immunization, she has used her celebrity to discourage parents from getting their kids immunized. This study has now been shown not only to have been methodologically shaky but to have had some of the facts fabricated. The blog The Incidental Economist has a good review of it here:

The Autism/MMR Fraud | The Incidental Economist

Ms. McCarthy and her followers may have been sincere in wanting to protect children from Autism and it is sad that they have been mislead into doing more harm than good. Even if the study had not been fraudulent, extreme caution would be needed to establish a causal link between Autism and the MMR vaccine. They followed 12 children after being vaccinated. It's hard to make any generalizations from that small of a sample. I could go on and on about problems with this study but there are lots of larger more sound studies that lead many otherwise brilliant people jump to conclusions about cause and effect (especially when it justifies what they already believe).

Merely establishing an association between two variables does not establish a cause and effect relationship between the two. In my post Income and Life Expectancy. What does it Tell Us About US? the video from the documentary The Joy of Stats compellingly shows an association between income adjusted per person and life expectancy over 200 years in 200 countries. It is tempting to infer that there is a cause and effect relationship between wealth and life expectancy. However even here there are many potential third variables such as with what is that wealth used to purchase? My analysis in that post should shed light on some of those complexities. Stephen Colbert has a humorous take on this fallacy by spoofing Glenn Beck's promotion of gold on his program.

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The best way to determine cause and effect relationships is in an experiment. Ideally an experiment is a study where every variable is controlled and accounted for by the researcher in a treatment group and a comparison group. Unknown variables are controlled for by randomly assigning patients or subjects to groups.

When it comes to autism and the MMR vaccine, it is neither practical nor ethical to do an experiment to see if there's a causal relationship. Experiments are often done on animals first when feasible but for mental disorders like autism or schizophrenia there is no good animal model. Correlational studies are often the best that can be done. It's hard enough to interpret even when the study is not fraudulent.

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