Solutions - Case Study: Published Papers and Studies
Part One: Abstracts
Each of the following represents an abstract - a.k.a., a summary paragraph - for a real published study. For each, briefly answer the following questions. You may not be able to find the answers to every question in every abstract; if it is not explicitly stated, make a guess, such as, “They probably used a placebo.”
Is this an experiment or an observational study?
If it is an experiment:
What are subjects/experimental units?
What are the treatments?
What variable measures the outcome?
Did they use blinding?
Was there any blocking?
If it is an observational study:
What are the cases?
What are the variables?
What was the sampling method?
Can you think of any possible lurking variables?
What were the conclusions?
Did they share any summary statistics?
Can they make a causal claim?
Effect of thawing conditions and corresponding frying temperature profiles on the formation of acrylamide in French fries
(fries?)
This study attempted to determine the effects of thawing conditions and corresponding frying temperature profiles on the formation of acrylamide in French fries. Frozen par-fried potato strips were thawed under three different conditions, at room temperature, using a chiller, and using a microwave. Unthawed par-fried potato strips were used as the control samples. Thawed (or unthawed) par-fried potato strips were deep-fat fried in palm oil at 180 ± 5 °C for 3.5 min. The temperature drop was monitored every 15 s for a total of 6 min; 3.5 min of frying time plus an additional 2.5 min until the oil temperature returned to 180 °C. The acrylamide content, oil content and colour of the French fries were measured. The frying temperature dropped substantially (more than 30 °C) from the initial temperature in the first 45 s of frying for all thawing conditions. After 90 s of frying, the smallest temperature drops were observed for French fries thawed using a microwave (20%), and the largest temperature drop prior to recovery was seen with the control sample (24%). At the end of the frying period (after 210 s), French fries thawed using a microwave had reached the highest final temperature (154 °C), and the control sample had reached the lowest final temperature (145 °C). The acrylamide contents of the French fries were found to be in the range of 77.4–106 ng/g, whereas the oil contents ranged from 16.4 to 20.5%. The lowest lightness, highest redness and highest yellowness were found for French fries thawed using a microwave. Although the thawing conditions did not significantly affect the formation of acrylamide, microwave thawing was found to be the best thawing method due to the resulting (relatively) low acrylamide and oil contents of the French fries and their desirable colour attributes. The results of this study can be used to recommend that the manufacturers of frozen par-fried potato strips specify the use of a microwave for thawing as part of the frying instruction on the packaging.
Solution
This is an experiment.
The subjects were the potato strips. The treatments were: thawed at room temperature, thawed using a chiller, thawed using a microwave, and unthawed.
The outcome variable was the speed of temperature drop. (Other outcome variables: acrylamide, color, oil content)
They did not use blinding on the subjects, of course. It is not stated if they used blinding on the researchers; presumably yes.
No blocking was reported in the study.
They shared summary statistics on:
Average temperature at various time points
Average temperature percent decrease after 90 seconds
Range of acrylamide content
Range of oil content
They can make causal claims, because this is an experiment that used randomization.
Habitat Selection of Breeding Birds in an East Tennessee Deciduous Forest
(birdpop?)
Bird populations were sampled between May 30 and July 20, 1972, on twenty-four 0.08-ha plots on Walker Branch Watershed, a primarily deciduous forest located in Anderson County, Tennessee. Univariate analysis of variance was used to test for differences in abundance categories of each bird species with respect to 28 habitat variables. Differences in habitat preferences within major bird families (Picidae, Parulidae, Paridae, and Thraupidae) were apparent from this analysis. Discriminant function analysis was therefore used to order the variables according to their strength in separating abundance categories for 13 of the more abundant bird species. This analysis indicated that some bird species were distributed according to specific habitat variables. For example, Downy Woodpecker abundance was highly correlated with the number of saplings on a plot. Distributions of other species (e.g., the Scarlet Tanager) were not strongly related to any single variable but were related weakly to a large number of variables. The results form a basis for predicting avifaunal composition changes resulting from alteration of habitat structure.
Solution
This is an observational study.
The cases were the locations.
The variables were:
Abundance of various bird types (e.g. Downy Woodpecker and Scarlet Tanager)
Abundance of various plant types (only saplings is mentioned specifically)
Possibly other measurements about the ecology of the plot of land
The sampling method was probably simple random sample of plots from the whole land area.
Possible lurking variables could be things like: number of predators in that area, climate/temperature in the locations where researchers were able to observe, difficulty of finding birds in habitats with thicker foliage.
They did not report any specific statistics. (Although they imply a nonzero correlation between saplings and Downy Woodpeckers.)
They can not make causal claims, since this is an observational study.
Defensive Behavior of Cottonmouths (Agkistrodon piscivorus) toward Humans
Venomous snakes are often perceived as aggressive antagonists, with the North American cottonmouth having a particularly notorious reputation for such villainy. We designed tests to measure the suite of behavioral responses by free-ranging cottonmouths to encounters with humans. When confronted, 23 (51%) of 45 tested tried to escape, and 28 (78%) of 36 tested used threat displays and other defensive tactics; only 13 of 36 cottonmouths bit an artificial hand used in the tests. Our findings challenge conventional wisdom about aggressive behavior in an animal perceived as more dangerous than it is. Changing irrational negative attitudes about venomous snakes is a necessary step toward quelling the recently documented global decline in reptiles.
Solution
This can be regarded as:
- An experiment with one treatment, moving an artificial hand near the snakes.
- An observational study
The subjects were the snakes.
The (outcome) variable measured was response to artificial hand.
The summary statistic reported is the percent of snakes that tried to escape, used threat displays, or bit the hand.
They can not make causal claims, because there is not randomization across treatments.
Computer animations stimulate contagious yawning in chimpanzees
(chimps?)
People empathize with fictional displays of behaviour, including those of cartoons and computer animations, even though the stimuli are obviously artificial. However, the extent to which other animals also may respond empathetically to animations has yet to be determined. Animations provide a potentially useful tool for exploring non-human behaviour, cognition and empathy because computer-generated stimuli offer complete control over variables and the ability to program stimuli that could not be captured on video. Establishing computer animations as a viable tool requires that non-human subjects identify with and respond to animations in a way similar to the way they do to images of actual conspecifics. Contagious yawning has been linked to empathy and poses a good test of involuntary identification and motor mimicry. We presented 24 chimpanzees with three-dimensional computer-animated chimpanzees yawning or displaying control mouth movements. The apes yawned significantly more in response to the yawn animations than to the controls, implying identification with the animations. These results support the phenomenon of contagious yawning in chimpanzees and suggest an empathic response to animations. Understanding how chimpanzees connect with animations, to both empathize and imitate, may help us to understand how humans do the same.
Solution
This is an experiment.
The subjects are the chimpanzees. The treatments were showing the chimps an animated yawn video, or not.
The outcome variable is how many times the chimps yawned.
There was no blinding.
There was no reported blocking.
No specific summary statistics were reported.
They can make causal claims, assuming the chimps were randomly assigned to the treatments.
A Controlled Trial of Arthroscopic Surgery for Osteoarthritis of the Knee
(knee?)
BACKGROUND
Many patients report symptomatic relief after undergoing arthroscopy of the knee for osteoarthritis, but it is unclear how the procedure achieves this result. We conducted a randomized, placebo-controlled trial to evaluate the efficacy of arthroscopy for osteoarthritis of the knee.
METHODS
A total of 180 patients with osteoarthritis of the knee were randomly assigned to receive arthroscopic débridement, arthroscopic lavage, or placebo surgery. Patients in the placebo group received skin incisions and underwent a simulated débridement without insertion of the arthroscope. Patients and assessors of outcome were blinded to the treatment-group assignment. Outcomes were assessed at multiple points over a 24-month period with the use of five self-reported scores — three on scales for pain and two on scales for function — and one objective test of walking and stair climbing. A total of 165 patients completed the trial.
RESULTS
At no point did either of the intervention groups report less pain or better function than the placebo group. For example, mean (±SD) scores on the Knee-Specific Pain Scale (range, 0 to 100, with higher scores indicating more severe pain) were similar in the placebo, lavage, and débridement groups: 48.9±21.9, 54.8±19.8, and 51.7±22.4, respectively, at one year (P=0.14 for the comparison between placebo and lavage; P=0.51 for the comparison between placebo and débridement) and 51.6±23.7, 53.7±23.7, and 51.4±23.2, respectively, at two years (P=0.64 and P=0.96, respectively). Furthermore, the 95 percent confidence intervals for the differences between the placebo group and the intervention groups exclude any clinically meaningful difference.
CONCLUSIONS
In this controlled trial involving patients with osteoarthritis of the knee, the outcomes after arthroscopic lavage or arthroscopic débridement were no better than those after a placebo procedure.
Solution
This is an experiment.
The subjects are patients with osteoarthiritis. The treatments are arthroscopic lavage, arthroscopic debridement, and placebo procedure.
The outcome variables were five self-reported pain and function scores, measured at multiple time points.
Blinding was used on the subjects with the placebo procedure. It is not stated whether blinding was used on the researchers conducting the outcome interviews; hopefull yes.
No blocking was reported. (Although it seems likely that an experiment like this may have blocked for gender, age, etc.)
They reported the mean (and margin of error) pain scores at each time point for each treatment group.
They can not make causal claims, because althouhg this was an experiment with randomization, they did not actually observe a significant difference across treatment groups.
Stream buffers ameliorate the effects of timber harvest on amphibians in the Cascade Range of Southern Washington, USA
We addressed the efficacy of stream-side buffers in ameliorating the effects of clearcut timber harvest on Cascade torrent salamanders (Rhyacotriton cascadae), coastal/Cope’s giant salamanders (Dicamptodon tenebrosus/D. copei), coastal tailed frogs (Ascaphus truei), and water temperature regimes in the Cascade Range in southern Washington. Forty-one streams in 4 categories were sampled; streams in clearcuts with and without buffers, streams in 35+ year old second-growth forest, and streams in unharvested forest (150+ years old). Tailed frog and Cascade torrent salamander densities were 2–7-fold lower (P < 0.05), respectively, in streams in managed forests than in streams in unharvested forest. In addition, both these species were less abundant (P < 0.05) in unbuffered streams than streams with buffers or in second-growth forest. In contrast, giant salamander densities were 5–50% greater (P > 0.05) in managed streams than unharvested, being greatest in unbuffered and second-growth streams. We used the differences in density estimates of unbuffered streams and unharvested streams to define an ecologically important effect size for each species and then compared the mean effect size and 95% confidence intervals of contrasts between managed stream categories to assess buffer effectiveness. Buffers had a positive ecologically important effect on the density of torrent salamanders and tailed frogs, but had an ecologically negative effect on giant salamanders. Water temperatures were similar among stream categories. However, Cascade torrent salamanders were nearly absent from streams where temperatures were ≥14 °C for ≥35 consecutive hours. Issues that need further study include effective buffer width and longitudinal extent, and confirmation of the water temperature threshold we identified.
Research highlights
This study found that stream buffers were effective in reducing the impact of clearcut harvest on 2 species of stream-associated amphibians in Washington. However, 1 species was more abundant in streams without buffers. We also identified a stream temperature regime that influenced stream occupancy by 1 species in terms of maximum temperature and duration, which has not been previously identified.
Solution
This is an observational study.
The cases were water samples taken from the streams.
The variables recorded were:
Abundance of Cascade torrent salamanders, coastal/Cope’s giant salamanders, and coastal tailed frogs
Temperature of water
Location of sample
The sampling method was a stratified sample - they observed streams in different types of locations, like old growth forest versus managed forest.
They reported:
Percent decreased in Cascade torrent salamander and frog abundance in managed vs. unharvested forests.
Percent increase in giant salamander abundance in managed vs. unharvested forests.
Cascade torrent salamander abundance of zero in streams with certain temperatures.
Part Two: Ethics
Below, you will find links to articles about famous experiments or
studies in history that are considered to be highly unethical.
For each, answer the following:
Were any participants unable to consent in their participation?
Did any of the subjects have their privacy violated?
Who was harmed by the study?
Who funded the study, and what did they gain from it?
Who designed and/or performed the study and analysis, and what did they gain from it?
Besides those involved in the study, who has benefitted from the results?
*Note: You should not have to read more than the first couple paragraphs of the
article to be able to answer these questions. However, feel free to read more -
they are fascinating parts of scientific history!*
- The Tuskeegee Syphillus Study: https://en.wikipedia.org/wiki/Tuskegee_Syphilis_Study
- Were any participants unable to consent in their participation?
Yes, the participants were not fully informed of the nature of the study, and they were also manipulated due to the offer of free health care to impoverished people.
- Did any of the subjects have their privacy violated?
Possibly, but this is not the main issue.
- Who was harmed by the study?
The subjects, who were deliberately not given treatment even though it existed.
The communities of the subjects, where syphilis spread because it wasn’t being prevented; also, these communities and families lost members when the subjects died.
- Who funded the study, and what did they gain from it?
The United States Public Health Service and the Center for Disease Control. They mainly gained knowledge about the disease.
- Who designed and/or performed the study and analysis, and what did they gain from it?
Tuskegee University doctors and researchers performed the study. Doctors were presumably paid for their expertise and medical skills, and academics presumably published results.
- Besides those involved in the study, who has benefitted from the results?
It’s possible that the knowledge of syphilis gained in this study has helped its treatment in future patients.
- The Stanford Prison Experiment: https://en.wikipedia.org/wiki/Stanford_prison_experiment
- Were any participants unable to consent in their participation?
Yes; although they consented to the initial study, they could not know the extent of what their experience would be, so it was not informed consent.
- Did any of the subjects have their privacy violated?
Possibly; the study is now very famous.
- Who was harmed by the study?
The subjects mainly.
Who funded the study, and what did they gain from it?
Who designed and/or performed the study and analysis, and what did they gain from it?
Philip Zimbardo’s lab funded and perfomed the study, and they gained the academic benefit of publication of results.
- Besides those involved in the study, who has benefitted from the results?
Unclear; perhaps some insight into authoritative brutality was gained.
- The Milgram Experiment: https://en.wikipedia.org/wiki/Milgram_experiment
- Were any participants unable to consent in their participation?
No, the electric shock was a fake, and the actual participants consented.
- Did any of the subjects have their privacy violated?
No.
- Who was harmed by the study?
The subjects, who were led to believe they were harming someone else.
Who funded the study, and what did they gain from it?
Who designed and/or performed the study and analysis, and what did they gain from it?
Stanley Milgram and his lab funded, designed, and performed the study. They gained academic benefit.
- Besides those involved in the study, who has benefitted from the results?
The results of this study have informed many future studies and psychological understanding of how people obey authority.
- Facebook’s User Emotions Experiment: https://www.theatlantic.com/technology/archive/2014/06/everything-we-know-about-facebooks-secret-mood-manipulation-experiment/373648/
- Were any participants unable to consent in their participation?
Yes, users were experimented on without their knowledge.
- Did any of the subjects have their privacy violated?
Yes, data from users Facebook accounts was analyzed without permission.
- Who was harmed by the study?
The users, who had their feed manipulated without their knowledge.
- Who funded the study, and what did they gain from it?
It appears that Facebook provided the resources to manipulate the News Feeds and collect the data. They gained information about how their users interact with their social network platform.
- Who designed and/or performed the study and analysis, and what did they gain from it?
Adam D. I. Kramer, Jamie E. Guillory, and Jeffrey T. Hancock are the credited authors on the published paper linked in the article.
- Besides those involved in the study, who has benefitted from the results?
This study helped spread information about how Facebook News Feeds can manipulate a person’s opinions and emotions, which has become a growing problem in recent years.