Wednesday, November 20, 2013
Retrieval Practice Produces More Learning than Elaborative Studying with Concept Mapping
Educators rely heavily on learning activities that encourage elaborative studying, whereas activities that require students to practice retrieving and reconstructing knowledge are used less frequently. Here, we show that practicing retrieval produces greater gains in meaningful learning than elaborative studying with concept mapping. The advantage of retrieval practice generalized across texts identical to those commonly found in science education. The advantage of retrieval practice was observed with test questions that assessed comprehension and required students to make inferences. The advantage of retrieval practice occurred even when the criterial test involved creating concept maps. Our findings support the theory that retrieval practice enhances learning by retrieval-specific mechanisms rather than by elaborative study processes. Retrieval practice is an effective tool to promote conceptual learning about science.
Sunday, January 1, 2012
entangled diamonds
OTTAWA -- An Ottawa physicist's team has "entangled" two diamonds, bringing the mysterious world of quantum physics to objects big enough to see.
Entanglement is a process in quantum mechanics by which two objects act like a single object even though they're not physically connected.
It usually involves very small objects -- atoms or molecules, for example.
Now Ben Sussman of the National Research Council has entangled objects far bigger than molecules -- pieces of diamond about half a millimetre thick. It's a step toward extremely fast quantum computing.
Sussman and his group write that "our intuition about the natural world" says quantum physics rules the tiny scale of atoms, while "classical" laws of motion cover objects big enough to see, such as cars or golf balls.
Quantum physics has been stretched to larger objects already, but there are usually special circumstances. For instance, scientists have used ultracold superconductors isolated from their surroundings.
These diamonds are large and operate at room temperature, some 15 centimetres apart. Sussman said they could, in principle, be even more distant. (He used synthetic diamonds to avoid impurities, but natural stones would work too.)
Entanglement contradicts what our senses tell us. It means two distinct objects have a relationship where a change in one means a simultaneous change in the other.
Physicists sometimes use the analogy of a teeter-totter: When one end goes up, the other has to go down at the same time.
But entangled objects aren't physically joined like the teeter-totter's two ends.
Einstein didn't like the concept; he called it "spooky action at a distance." Still, experiments show it's real.
The quantum world has captured popular imagination for decades with its puzzles. There's Edwin Schrodinger's cat, where the principle of uncertainty says the cat may be alive and dead at the same time.
There are possibilities of teleportation and time-travel -- staples of science fiction that always want to bend reality. The concept of entanglement leads to dreamy notions that everything is connected to everything else.
Now the reality of quantum mechanics is leading toward a more matter-of-fact goal: computers faster and more secure than anything made today.
Sussman's group used diamonds because they react to laser light by showing some characteristics of the quantum world, and their extreme hardness helps preserve that quantum character.
"This (entangled diamonds) is a state that simply can't be described with classical physics," Sussman said.
"There's great interest in understanding the transition between this microscopic world of quantum mechanics and our macroscopic world, which we live in every day."
What the diamonds shared "is a bit ethereal," Sussman said. "They shared a deep connection. They shared a vibration. They shared the same state. In a sense, these two objects shared each other. They became one... It's a bit romantic, but could be suitable, given that they're diamonds.
"They're both about steps toward quantum computing and are really fascinating because we've been able to make all this microscopic quantum stuff exist at large sizes (millimetres) and at room temperature," he said.
"I've been using the idea of building on our 'quantum workbench' -- something quantum that you can really get your hands on."
Entanglement is a process in quantum mechanics by which two objects act like a single object even though they're not physically connected.
It usually involves very small objects -- atoms or molecules, for example.
Now Ben Sussman of the National Research Council has entangled objects far bigger than molecules -- pieces of diamond about half a millimetre thick. It's a step toward extremely fast quantum computing.
Sussman and his group write that "our intuition about the natural world" says quantum physics rules the tiny scale of atoms, while "classical" laws of motion cover objects big enough to see, such as cars or golf balls.
Quantum physics has been stretched to larger objects already, but there are usually special circumstances. For instance, scientists have used ultracold superconductors isolated from their surroundings.
These diamonds are large and operate at room temperature, some 15 centimetres apart. Sussman said they could, in principle, be even more distant. (He used synthetic diamonds to avoid impurities, but natural stones would work too.)
Entanglement contradicts what our senses tell us. It means two distinct objects have a relationship where a change in one means a simultaneous change in the other.
Physicists sometimes use the analogy of a teeter-totter: When one end goes up, the other has to go down at the same time.
But entangled objects aren't physically joined like the teeter-totter's two ends.
Einstein didn't like the concept; he called it "spooky action at a distance." Still, experiments show it's real.
The quantum world has captured popular imagination for decades with its puzzles. There's Edwin Schrodinger's cat, where the principle of uncertainty says the cat may be alive and dead at the same time.
There are possibilities of teleportation and time-travel -- staples of science fiction that always want to bend reality. The concept of entanglement leads to dreamy notions that everything is connected to everything else.
Now the reality of quantum mechanics is leading toward a more matter-of-fact goal: computers faster and more secure than anything made today.
Sussman's group used diamonds because they react to laser light by showing some characteristics of the quantum world, and their extreme hardness helps preserve that quantum character.
"This (entangled diamonds) is a state that simply can't be described with classical physics," Sussman said.
"There's great interest in understanding the transition between this microscopic world of quantum mechanics and our macroscopic world, which we live in every day."
What the diamonds shared "is a bit ethereal," Sussman said. "They shared a deep connection. They shared a vibration. They shared the same state. In a sense, these two objects shared each other. They became one... It's a bit romantic, but could be suitable, given that they're diamonds.
"They're both about steps toward quantum computing and are really fascinating because we've been able to make all this microscopic quantum stuff exist at large sizes (millimetres) and at room temperature," he said.
"I've been using the idea of building on our 'quantum workbench' -- something quantum that you can really get your hands on."
Wednesday, November 17, 2010
Pain Prevalence Increases at the End of Life
The prevalence of pain increases rapidly in the last few months of life, regardless of the cause of death, a study in the Annals of Internal Medicine reports.
Researchers used data from the national Health and Retirement Study to examine levels of pain in some 4700 people over age 50 who died within 24 months of being interviewed about their pain levels. The participants were placed within 24 groups, according to the time span between their interviews and death.
Clinically significant pain — defined as pain of moderate or severe intensity most of the time — was present in about one quarter of the patients over the first 20 months. However, starting about 4 months before death, the prevalence of clinically significant pain began rising steadily, reaching a prevalence of about 50% in the final month of life. (The rate reached 60% among those with arthritis.)
An editorialist advises clinicians to routinely ask about clinically significant pain and be prepared to treat it.
Researchers used data from the national Health and Retirement Study to examine levels of pain in some 4700 people over age 50 who died within 24 months of being interviewed about their pain levels. The participants were placed within 24 groups, according to the time span between their interviews and death.
Clinically significant pain — defined as pain of moderate or severe intensity most of the time — was present in about one quarter of the patients over the first 20 months. However, starting about 4 months before death, the prevalence of clinically significant pain began rising steadily, reaching a prevalence of about 50% in the final month of life. (The rate reached 60% among those with arthritis.)
An editorialist advises clinicians to routinely ask about clinically significant pain and be prepared to treat it.
Saturday, August 28, 2010
MP3 Players Associated with Short-Term Hearing Loss
Listening to an MP3 player for just an hour can lead to temporary hearing loss, according to a small study in the Archives of Otolaryngology—Head & Neck Surgery.
Researchers in Belgium had 21 young adults with normal hearing listen to pop rock on an MP3 player at comfortable volumes for an hour, on six different occasions at least 2 days apart. The researchers found that, after listening, subjects experienced significant deterioration in hearing at high and low frequencies. Analyses revealed that hearing loss was temporary — participants recovered their normal hearing in between listening sessions.
The authors call for more research but say their findings "indicate the potential harmful effects" of listening to MP3 players.
Researchers in Belgium had 21 young adults with normal hearing listen to pop rock on an MP3 player at comfortable volumes for an hour, on six different occasions at least 2 days apart. The researchers found that, after listening, subjects experienced significant deterioration in hearing at high and low frequencies. Analyses revealed that hearing loss was temporary — participants recovered their normal hearing in between listening sessions.
The authors call for more research but say their findings "indicate the potential harmful effects" of listening to MP3 players.
Thursday, August 19, 2010
experimental data
Intention to Treat Analysis
P-value
Confidence Interval
Absolute Risk Reduction or Relative Risk Reduction
Number Need to Treat an Number Need to Harm
Odds Ratio
When looking at the results it is important to understand if an intention to treat analysis was applied. An intention to treat analysis is a statistical analysis of all the patients that started the trial, regardless of whether they were in the treatment or placebo group, or completed the trial. For instance, consideration should be given when there are 150 patients in the treatment group and 150 patients in the placebo group, but 50 patients in the treatment group drop-out half-way through the trial because of side effects. In this situation, it would be biased to look at just the 100 patients in the treatment group left at the end of trial and then artificially report a favourable benefit/risk profile for the treatment. However, when equal numbers of patients drop out in both groups, for known and unknown reasons, then the results are likely to be more valid. An intention to treat analysis, therefore maintains the integrity of the randomization process, reveals the similarities/differences between groups and attempts to provide a likely scenario of what would happen if this intervention was implemented in clinical practice.86
A p-value of ≤ 0.05 (or 1 divided by 20) means that if the trial was repeated 20 times that the results of 1 of those trials would probably be due to chance. A p-value of ≤ 0.05 is often acceptable and gives credence to the strength of the results but not the magnitude of treatment effect.
To understand the true treatment effect the confidence interval (CI) should be reported. The CI is expressed as a percentage of the likelihood that the treatment effect lays within a specified range. For instance, if 50% of the patients were likely to benefit from the treatment, and a 95% CI (40% to 60%) was reported, this means you can be confident 95% of the time that the treatment effect would lie within this range. A reporting of 50% is therefore a point estimate where it could be as low as 40% or as high 60% reasonable to expect a treatment effect of 50%. It is generally satisfactory to have a 95% CI with a tight range. However, any time a zero is reported in the interval range, you cannot assume the treatment effect to be true.85
The treatment effect can be reported as an absolute risk reduction (ARR) or relative risk reduction (RRR). For example, in a scenario where stroke occurred in 2% of patients (2 out of 100) given active treatment to lower blood pressure versus 4% of patients (4 out of 100) given placebo over a 5 year-period: a relative risk reduction of 50% (2% divided by 4%) or absolute risk reduction of 2% (4%-2%) could be reported. The magnitude of the RRR obviously looks much more significant than the ARR. However, what you want to know in this case is the number need to treat (NNT), which is 1 divided by the ARR. In this case you would get a NNT of 50 (1/.02) , which means you would have to give the blood pressure treatment to 50 patients for 5 years before you prevented 1 patient from having a stroke. The number need to harm (NNH) is calculated in the same way and tells you what the harm would be and how many patients you would have to give the treatment to before you saw 1 patient being harmed in that specific way. Obviously, you could then compare the NNT to NNH to understand the benefits versus the risks but the key is to have confidence in the results or a 95% CI or higher.86
It should be noted that in some instances the results are reported as an odds ratio (OR), which is comparable but not identical to the relative risk reduction. The OR is typically used in case control studies to assess risk of an adverse event or in cohort studies to assess disease outcome. The OR is calculated by dividing the number of occurrences in the intervention/treatment group by the number of occurrences in the control group. For instance, if an adverse effect of a drug is reported as an OR of 1.0 this means that the number of events in treatment group where equal to number of events in the placebo group. Similarly, if an adverse effect of drug is reported as an OR of 1.0, this means that the number of events in the treatment group were equal to number of events in the placebo group. Similarly, if an adverse effect of a drug is reported as an OR of greater than 1, this means that more individuals experienced an event in the treatment group compared to the placebo group. Therefore, an OR of less than 1 in this case means that the number of individuals in the treatment group that experienced an adverse effect was less than the placebo group.86
Taking this one step further, let’s say a particular treatment effect on reducing colds was reported as an OR of 0.42 with 95% CI of 0.25-0.71 and p<0.001. It is therefore accurate to say that the intervention group experienced a 58% (calculated as 1-0.42 X 100) reduction in catching a cold compared to the placebo group. However, regardless of whether the OR or RRR is used the CI and p-value should be reported in order for the trial outcome to be viewed as reliable. The NNT and NNH is not as easily calculated for OR because it requires a much more involved mathematical formula or can be estimated using tables.
P-value
Confidence Interval
Absolute Risk Reduction or Relative Risk Reduction
Number Need to Treat an Number Need to Harm
Odds Ratio
When looking at the results it is important to understand if an intention to treat analysis was applied. An intention to treat analysis is a statistical analysis of all the patients that started the trial, regardless of whether they were in the treatment or placebo group, or completed the trial. For instance, consideration should be given when there are 150 patients in the treatment group and 150 patients in the placebo group, but 50 patients in the treatment group drop-out half-way through the trial because of side effects. In this situation, it would be biased to look at just the 100 patients in the treatment group left at the end of trial and then artificially report a favourable benefit/risk profile for the treatment. However, when equal numbers of patients drop out in both groups, for known and unknown reasons, then the results are likely to be more valid. An intention to treat analysis, therefore maintains the integrity of the randomization process, reveals the similarities/differences between groups and attempts to provide a likely scenario of what would happen if this intervention was implemented in clinical practice.86
A p-value of ≤ 0.05 (or 1 divided by 20) means that if the trial was repeated 20 times that the results of 1 of those trials would probably be due to chance. A p-value of ≤ 0.05 is often acceptable and gives credence to the strength of the results but not the magnitude of treatment effect.
To understand the true treatment effect the confidence interval (CI) should be reported. The CI is expressed as a percentage of the likelihood that the treatment effect lays within a specified range. For instance, if 50% of the patients were likely to benefit from the treatment, and a 95% CI (40% to 60%) was reported, this means you can be confident 95% of the time that the treatment effect would lie within this range. A reporting of 50% is therefore a point estimate where it could be as low as 40% or as high 60% reasonable to expect a treatment effect of 50%. It is generally satisfactory to have a 95% CI with a tight range. However, any time a zero is reported in the interval range, you cannot assume the treatment effect to be true.85
The treatment effect can be reported as an absolute risk reduction (ARR) or relative risk reduction (RRR). For example, in a scenario where stroke occurred in 2% of patients (2 out of 100) given active treatment to lower blood pressure versus 4% of patients (4 out of 100) given placebo over a 5 year-period: a relative risk reduction of 50% (2% divided by 4%) or absolute risk reduction of 2% (4%-2%) could be reported. The magnitude of the RRR obviously looks much more significant than the ARR. However, what you want to know in this case is the number need to treat (NNT), which is 1 divided by the ARR. In this case you would get a NNT of 50 (1/.02) , which means you would have to give the blood pressure treatment to 50 patients for 5 years before you prevented 1 patient from having a stroke. The number need to harm (NNH) is calculated in the same way and tells you what the harm would be and how many patients you would have to give the treatment to before you saw 1 patient being harmed in that specific way. Obviously, you could then compare the NNT to NNH to understand the benefits versus the risks but the key is to have confidence in the results or a 95% CI or higher.86
It should be noted that in some instances the results are reported as an odds ratio (OR), which is comparable but not identical to the relative risk reduction. The OR is typically used in case control studies to assess risk of an adverse event or in cohort studies to assess disease outcome. The OR is calculated by dividing the number of occurrences in the intervention/treatment group by the number of occurrences in the control group. For instance, if an adverse effect of a drug is reported as an OR of 1.0 this means that the number of events in treatment group where equal to number of events in the placebo group. Similarly, if an adverse effect of drug is reported as an OR of 1.0, this means that the number of events in the treatment group were equal to number of events in the placebo group. Similarly, if an adverse effect of a drug is reported as an OR of greater than 1, this means that more individuals experienced an event in the treatment group compared to the placebo group. Therefore, an OR of less than 1 in this case means that the number of individuals in the treatment group that experienced an adverse effect was less than the placebo group.86
Taking this one step further, let’s say a particular treatment effect on reducing colds was reported as an OR of 0.42 with 95% CI of 0.25-0.71 and p<0.001. It is therefore accurate to say that the intervention group experienced a 58% (calculated as 1-0.42 X 100) reduction in catching a cold compared to the placebo group. However, regardless of whether the OR or RRR is used the CI and p-value should be reported in order for the trial outcome to be viewed as reliable. The NNT and NNH is not as easily calculated for OR because it requires a much more involved mathematical formula or can be estimated using tables.
Wednesday, June 2, 2010
cervical cancer and what do the experts know
The medically accepted paradigm, officially endorsed by the American Cancer Society and other organizations, is that a patient must have been infected with HPV to develop cervical cancer, and is hence viewed as a sexually transmitted disease, but most women infected with high risk HPV will not develop cervical cancer.[16] ANDThe widespread introduction of the Papanicolaou test, or Pap smear for cervical cancer screening has been credited with dramatically reducing the incidence and mortality of cervical cancer in developed countries.[8] BUT... Some 1100 clinicians (internists, family practitioners, or obstetrician-gynecologists) were given a series of clinical vignettes that described women by age, sexual experience, and Pap testing history. Participants provided their screening recommendations for each scenario.While over 80% said that at least one set of screening guidelines (e.g., U.S. Preventive Services Task Force) was "very influential" in their practices, only 22% recommended guideline-consistent care for every vignette. Obstetrician-gynecologists were less guideline-concordant than the other specialties.Of note, one third of participants recommended annual Pap testing for an 18-year-old who hadn't had sexual intercourse, while almost half continued to recommend Pap testing for a women whose cervix had been removed for benign reasons.
The most important risk factor in the development of cervical cancer is infection with a high-risk strain of human papillomavirus. The virus cancer link works by triggering alterations in the cells of the cervix, which can lead to the development of cervical intraepithelial neoplasia, which can lead to cancer. Women who have many sexual partners (or who have sex with men who had many other partners) have a greater risk.[10][11]
The most important risk factor in the development of cervical cancer is infection with a high-risk strain of human papillomavirus. The virus cancer link works by triggering alterations in the cells of the cervix, which can lead to the development of cervical intraepithelial neoplasia, which can lead to cancer. Women who have many sexual partners (or who have sex with men who had many other partners) have a greater risk.[10][11]
Saturday, May 22, 2010
pi theory
A theory can explain, predict and be used for technological applications and still be wrong. This is analogous to thinking pi as a rational number. 22/7 is a close approximate and may even be useful in many applications, BUT ITS WRONG. 339/108 is closer still but it too is wrong. Hence we can get extend a limit of reality ie get closer and closer but never get there.
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