CHYS 2P51 Chapter Notes - Chapter 4: Systematic Sampling, Sampling Bias, Convenience Sampling

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ceruleanwalrus53

5 Oct 2013

School

Brock University

Department

Child and Youth Studies

Course

CHYS 2P51

Professor

Jan Frijters

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Document Summary

When other people begin to get involved in the research process (participants, and the people who will be influenced by the study if they read it) the researchers needs to consider ethical issues. Two categories of ethical responsibility: 1) ensuring the welfare and dignity (of participants: human or not, 2) ensuring public records of research are accurate and honest. Human participants: before ww2 the ethical standards were set by each researcher, historical examples (p. 110) Apa guidelines (p. 114-116: guidelines because it is impossible to predict every type of study being done in the future they intend to identify, contains 10 ethical standards the most important for new researchers are: Human participants should be given complete information about the research and their roles in it before agreeing to participate. Information: to not risk sabotaging the experiment, researchers may tell the participant what is exactly going to happen in the study, but not why: are informed of any potential risks though.

Related Questions

Imagine that researchers are conducting a randomized controlled trial of a high-fiber supplement as a preventive measure in persons at increased risk of type 2 diabetes. People enrolled in the study are disease-free at the time they agree to participate in the trial, but they all have a family history of type 2 diabetes and are considered at high-risk (80%) to develop the disease during their lifetime. The 10,000 participants who start the trial are healthy individuals who are randomly allocated to receive either high-fiber supplements or placebo for several years. As you can imagine, this study will be quite expensive and will require a large infrastructure of personnel and materials to carry it out successfully.

Because type 2 diabetes has reached epidemic proportions in the United States, the potential benefits of this research are important at a population level. Unfortunately, high-fiber supplements have also been shown in a few studies to be associated with gastrointestinal blockage (which can be life-threatening) and reduced nutrient absorption, which may lead to anemia, osteoporosis, and other debilitating chronic diseases. The supplements may also reduce absorption of certain medications and cause gastrointestinal distress. The potential side effects of continuous high-fiber supplementation are only partially understood, and long-term effects are unknown.

1. What are the potential risks and benefits to be considered when designing this study?

2. When the side effects and long-term effects of a potential preventive measure are largely unknown, is it ethical to expose participants to these risks? Why or why not?

3. Is it ethical to deny the possible prevention benefits of high-fiber supplements to persons in the placebo group? Why or why not?

I think since the

4. Do the potential benefits outweigh the potential risks to the participants and to society? Why or why not?

In a small paragraph, compare and summarize these two articles.

Article 1 Description

This article is an observational study, which discusses how frequency dependent selection affects two phenotypes of a predator through differential guarding response. The researcher examines the ratio of handedness of two samples of P. microlepis collected from two adjacent sites along Lake Tanganyikaâs northwestern shoreline for a period of eleven years. The process of observations includes observing the correspondence between the handedness of P. microlepis and their targeted prey (Hori, 1993). The researcher carried observations to identify the direction from which P. microlepis attacked the flank of their prey. Moreover, the researcher used a gill net to catch each P. microlepis that attacked the lure. Catching the P. microbes made it possible for the researcher to observe its features and determine its handedness. The researcher determined the handedness of the scales of P. microlepis by observing the fish under a microscope.

During the period of study, Hori (1993) established that the ratio of handedness of P. microbes remained at 0.5 for each one-to-two year intervals throughout the eleven years of the study. Further investigations on temporal changes in handedness ratio showed that the ratio oscillated with amplitude of 0.15 within a five-year period (Hori, 1993). These observations were made for the two species of P. microlepis under investigation. The researcher concludes that the direction of mouth opening of scale eating cichlid fish in Lake Tanganyika is determined by the genetics of the fish. The researcher demonstrates that frequency-dependent natural selection determines the number of left-handedness or right-handedness fish. Based on researcherâs observations, when right-handed fish attack from behind, they snatch the scales from their prey from the left flank (Hori, 1993). On the other hand, when left-handed fish attack their prey from behind, they attack the right flank (Hori, 1993). Therefore, fish with rare phenotypes are more successful as predators than ones that have the more predominant phenotype. This study can be used to guide researchers who are interested in seeking ways of increasing the population of different species of fish. It can also be used as a basis for investigations on how fish type determines its survival tactics or predator tactics.

Article 2 Description

The study was an experimental analysis which sought to quantify phosphoglucose isomerase (Pgi) frequency change over a period of time and compare Pgi genotypes based on physiological responses to high temperatures and subzero thermal extremes encountered by beetles in nature. The research seeks to establish how the local climate in Bishop relates to changes in allele frequency at Pgi and other allozyme loci. It also seeks to establish if ambient temperature of beetle habitants rise to levels that expose beetles to stressful temperature. The researcher also seeks to establish how Pgi genotypes differ physiologically when exposed to subzero temperatures. By answering these questions, the researcher will establish the relationship between changes in enzyme genotype frequency and regional climate changes in addition to investigating major physiological mechanisms through which animals respond to change in climate.

To answer research questions and test research hypothesis, the researchers carried out several experiments and analyses of data. The experimental study involved collecting adult beetles that had emergent recently from pupae for a period of one year between August 1988 and August 1989 (Rank & Dahlhoff, 2002). Their genotype was determined at five different polymorphic enzyme loci. Some of the things analyzed during the study include fluctuations in climate and allele frequency change; daily and annual mean values of air temperature, Effects of Pgi genotype on HSP70 expression, and quantification of Pgi genotype on HSP70 expression among other things (Rank & Dahlhoff, 2002). The study results revealed that although beetle populations were genetically different the FST-values for 1996 were greater for each enzyme locus than those for 1998 (Rank & Dahlhoff, 2002). Moreover, researchers established that the frequency of Pgi allele had increased by 11 percent, a trend that was not observed for all the other loci investigated. Therefore, the researchers conclude that Pgi genotype differences in thermal physiology account for Pgi allele frequency change in nature. Contrary to selected hypothesis that the frequency of Pgi allele should increase with decrease in temperature, the study established that the frequency of Pgi allele decrease with decrease in temperature. This work is important because it provides a basis for more research on how variations in temperature affect beetle populations. The study findings can be used to guide researchers who are interested in seeking ways of protecting endangered beetle populations in different climatic conditions.

The Scientific Method

For any controlled scientific study, a scientist starts with an observation, does some research to develop a hypothesis, and then designs an experiment that compares some baseline group with a test group. Data are then collected to confirm or refute the hypothesis.

As you review the following study, consider whether the researchers correctly followed the scientific method.

In the late 1990s, gastroenterologist Andrew Wakefield, along with a research team, set out to determine if bowel disease caused by vaccines led to autism.

He compiled a group of 12 children who had loss of acquired skills, developmental delays in language, diarrhea, and abdominal pain-essentially, those with both bowel disease and autism. He questioned each parent about the behavior and personality of the child before the child was vaccinated with the Measles, Mumps, and Rubella (MMR) vaccine. He then ran tests on the children to determine the health of the gastrointestinal tract, brain, and nervous system.

His reported data (tabulated below) included that children experienced either gastrointestinal or autism-like symptoms, sometimes within a short period after being vaccinated. From these data, the researchers concluded that there was no link between autism and the MMR vaccine. Wakefield though, contradicted this conclusion and stated that the vaccine caused changes in the gastrointestinal tract of the children, which then led to autism (Wakefield, et al., 1998). Currently, he still contends that the MMR vaccine contributes to autism (Ziv, 2015).

Many researchers tried to duplicate this study and could not replicate Wakefield's results. In fact, they found no link between the vaccines, bowel disease, and autism. In the United Kingdom, the MMR vaccine was not introduced until 1988. If Wakefield's conclusions were correct, one would then expect a jump in autism cases after 1988, but this was not observed, even when hundreds of children were studied (Taylor et al., 1999). In these additional studies, children who had not been vaccinated were included as a control group, and no difference in the rates of autism was observed.

In 2011, Brian Deer reviewed Wakefield's study and all available records from the National Health Service (NHS) in the United Kingdom for these 12 children. He found that at most, two children showed symptoms days after vaccinations. At least five children showed developmental delays before being vaccinated. Six out of the 12 children may have had autism symptoms. None of the 12 children tested had all three-regressive autism, colitis, and symptoms days after vaccination.

Symptom	Wakefield	Wakefield NHS Records (Deer)
Symptoms days after vaccination	8	2?
Non-specific colitis	12	3
Regressive autism	9	6?
Intestinal/autism/symptoms after vaccine	12	0

(Wakefield, et al., 1998; Deer, 2011)

Wakefield's statements led to a worldwide panic about the safety of vaccines, but after Deer's report, Wakefield's study was retracted and his medical license was revoked for falsifying data. Click on the following links to review materials to enhance your knowledge of the scientific method and to support your analysis of Wakefield's experiment:

Steps of the Scientific Method: A simplified explanation of how the scientific method works, the steps taken to investigate phenomenon with diagrams

Do Vaccines Cause Autism?: A review of research demonstrating that vaccines and their components are not the cause of autism

Fifteen years after a vaccine scare, a measles epidemic: An analysis of vaccination trends and an increase in measles cases seen the UK

Answer the following 4 questions:

What was wrong with Wakefield's study? Discuss at least 1 variable or approach that should have been controlled or assessed.

Consider the source of some of his data (parental memory, for example), the small sample size, and whether he considered other variables (genetics, diet, and so on) that could have resulted in symptoms in these children.

Discuss the importance of a control group when using the scientific method.

Did Wakefield deserve to be barred from medical practice?

What were the consequences of his inflated conclusions?

CHYS 2P51 Chapter Notes - Chapter 4: Systematic Sampling, Sampling Bias, Convenience Sampling

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