Purposive Sampling Definition and Types

A purposive sample is a non-probability sample that is selected based on characteristics of a population and the objective of the study. Purposive sampling is different from convenience sampling and is also known as judgmental, selective, or subjective sampling. Purposive Sampling Types Maximum Variation/Heterogeneous Purposive SampleHomogeneous Purposive SampleTypical Case SamplingExtreme/Deviant Case SamplingCritical case SamplingTotal Population SamplingExpert Sampling This type of sampling can be very useful in situations when you need to reach a targeted sample quickly, and where sampling for proportionality is not the main concern. There are seven types of purposive samples, each appropriate to a different research objective. Types of Purposive Samples Maximum Variation/Heterogeneous A maximum variation/heterogeneous purposive sample is one which is selected to provide a diverse range of cases relevant to a particular phenomenon or event. The purpose of this kind of sample design is to provide as much insight as possible into the event or phenomenon under examination. For example, when conducting a street poll about an issue, a researcher would want to ensure that he or she speaks with as many different kinds of people as possible in order to construct a robust view of the issue from the publics perspective. Homogeneous A homogeneous purposive sample is one that is selected for having a shared characteristic or set of characteristics. For example, a team of researchers wanted to understand what the significance of white skin—whiteness—means to white people, so they asked white people about this. This is a homogenous sample created on the basis of race. Typical Case Sampling Typical case sampling is a type of purposive sampling useful when a researcher wants to study a phenomenon or trend as it relates to what are considered typical or average members of the effected population. If a researcher wants to study how a type of educational curriculum affects the average student, then he or she choose to focus on average members of a student population. Extreme/Deviant Case Sampling Conversely, extreme/deviant case sampling is used when a researcher wants to study the outliers that diverge from the norm as regards a particular phenomenon, issue, or trend. By studying the deviant cases, researchers can often gain a better understanding of the more regular patterns of behavior. If a researcher wanted to understand the relationship between study habits and high academic achievement, he or she should purposively sample students considered high achievers. Critical Case Sampling Critical case sampling is a type of purposive sampling in which just one case is chosen for study because the researcher expects that studying it will reveal insights that can be applied to other like cases. When sociologist C.J. Pascoe wanted to study sexuality and gender identity develop among high school students, she selected what was considered to be an average high school in terms of population and family income, so that her findings from this case could be more generally applicable. Total Population Sampling With total population sampling a researcher chooses to examine the entire population that has one or more shared characteristics. This kind of purposive sampling technique is commonly used to generate reviews of events or experiences, which is to say, it is common to studies of particular groups within larger populations. Expert Sampling Expert sampling is a form of purposive sampling used when research requires one to capture knowledge rooted in a particular form of expertise. It is common to use this form of purposive sampling technique in the early stages of a research process, when the researcher is seeking to become better informed about the topic at hand before embarking on a study. Doing this kind of early-stage expert-based research can shape research questions and research design in important ways. Updated by Nicki Lisa Cole, Ph.D.

The Benefits Of Cancer Screenings - 766 Words

Janeska Mendez The benefits of cancer screenings Out of thousands of diseases in the world cancer is one of the many diseases found that can cause your body to eventually shut down and result in your death. It is a disease caused by a genetic mutation in your cells, causing you to become weak and unable to fight infections, this disease can be treated and cured by using a high degree of radiation called chemotherapy. Most people with a weak immune system aren t able to fight the disease for very long, so you might only be cured temporarily, the disease can come back if it has spread throughout your body. Routine cancer screenings leads to an early detection of the disease, giving you a higher chance of saving many lives. For any individual male or female there is a high risk of getting a disease based on their family history. Many people have opinions on the benefits of cancer screenings being harmful to a person s health, they say that over time the effects of high doses of radiation on the body can result in you slowly damaging your health. Said by Gilbert Welch, professor of medicine, we should be doing fewer screening mammograms, not more. Although the research of the effects of mammography may be true, having less screenings would lead to more dangers of getting a further progressed disease and having no chance of beating the disease. It isShow MoreRelatedThe Pros and Cons of Health Screening Essay1093 Words   |  5 PagesHealth screening according to Durojaiye, (2009) is a systematic application of a test or inquiry, to identify individuals at sufficient risk of a specific health problem to warrant further investigation of direct preventive action, among persons who have not sough t medical attention on account of symptoms of that problem. According to this definition the main aim of screening program is to detect disease or risk factor, among the general population, in order to implement earlier preventive or therapeuticRead MoreProstate Cancer And The American Cancer Society1529 Words   |  7 Pagesprostate cancer (Eggener, Cifu, Nabhan, 2015). In 2015, prostate cancer was the second most common cancer related cause of death among United States men (Eggener, et. al., 2015). While the majority of prostate cancers are slow growing with a 5-year survival rate of approximately 98%, statistics show that when prostate cancer is identified as metastatic, the 5-year survival rate dramatically drops down to 20-25% (Eggener, et. al., 2015). According to these numbers alone, it appears screening for prostateRead MoreImportance Of Cervical Cancer Screening1278 Words   |  6 Pages(USPSTF) recommends cervical cancer screening with cytology testing (also known as a Pap Smear) every three years in women ages 21 to 65 (U.S. Preventative Services Task Force [USPSTF], 2016a). The USPSTF has graded this recommendation with an â€Å"A† indicating that they have a high level of certainty that the screening will prove to be beneficial, rather than harmful to the patient (USPSTF, 2016a). However, if this patient would prefer to receive cervical cancer screening every five years, the USPSTFRead MoreRisks of PSA Testing Essay1595 Words   |  7 Pagesdeveloping cancer, and 10 ng/ml is a 50% risk of cancer. However, some men with normal PSA levels still have prostate cancer, while other men with high PSA levels do not. PSA levels increase with age often due to a higher prevalence of benign prostate hypertrophy (BPH). Therefore, no PSA cutoff can accurately guarantee that a man does not have prostate cancer. PSA blood levels are used for several different purposes such as to diagnose prostate cancer, evaluate treatment of prostate cancer, and toRead MoreIs Mammography A Type Of Radiologic Imaging Used For Early Detection And Diagnosis Of Breast Disease?1567 Words   |  7 Pagesdetection and diagnosis of breast disease in women† (American Cancer Society). Patients receive doses of radiation that are much larger than that of a chest x-ray. It is rarely noted, that the act, in and of itself, may contribute to the development of malignant cells. Dr. Samuel Epstein, one of the top cancer experts, explains that the premenopausal breast is highly sensitive to radiation, each 1 rad exposure increases breast cancer risk by about 1 percent. 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From 2002 to 2012, the occurrences of a breast cancer diagnosis remained at an even level, however the death rate from breast

Site Finding And Planning For Wind Farms Environmental Sciences Essay Free Essays

Finding a air current farm site is a juggle act where many, frequently conflicting, issues need to be considered and balanced before a determination to develop a possible site is taken. At the most basic degree, after set uping that the end product from a air current power undertaking can be sold at an acceptable monetary value, the following are the acerb trials for any possible development: 1.Is grid connexion probably to be cost effectual for the coveted size of development? 2. We will write a custom essay sample on Site Finding And Planning For Wind Farms Environmental Sciences Essay or any similar topic only for you Order Now Is the air current resource adequate? 3.Will the undertaking be able to obtain all the licenses necessary for the air current farm to be built? 4.Is entree to the site and building of the air current farm likely to be cost effectual? 5.Can the rights to the land be secured? A good outlook that the reply to all of the above trials will be positive is a pre-requisite for doing the investing necessary to gain a undertaking, although necessarily early determinations need to be made on uncomplete information. A Each of the issues is considered in a little more item below: Grid connexion When looking for a site, propinquity to a medium electromotive force grid is a good initial index that an appropriate connexion is practical. The following phase of the procedure is to keep treatments with the appropriate electrical authorization. A The consequences of such treatments will normally bespeak a cap, or a series of caps on the upper limit installed capacity at a possible site which are associated with increasingly more dearly-won grid connexion scenarios. A Some elaborate analysis by the electrical authorization, at the cost of the developer, may be necessary before even approximative figures are available. A The presence of merely a high electromotive force line near to a little or average air current farm may non be helpful as the cost of connexion to such a grid may be prohibitory. Wind Resource It is hard to generalize how best to measure the air current resource at a possible air current farm site when no site air current informations are available, as different states have markedly different air current governments. A Some general regulations, for which there are many noteworthy exclusions, are listed below: Good exposure, peculiarly in the prevailing air current way, will well better the resource at a site. The rate at which wind velocity reduces off from the countries of a site with the best exposure should non be underestimated. A An â€Å" ideal † hill would hold smooth inclines of about 17 A grades gradient. Steeper inclines do non give significant extra sweetening of the air current flow but can do separation of the flow which complicates the air current conditions at a site. A Low flora at and around a site retards the air current flow less than tall flora. A However, a site with good exposure and little trees is likely to turn out better than a site with hapless exposure and no trees. A Building licenses Key issues will change between parts and states but common sense indicates that countries with particular appellations are best avoided. A Low visibleness from cardinal countries of habitation or diversion is besides desirable. A If there are homes within a few 100 metres of the air current farm site noise or shadow spark may turn out an insurmountable job in some states. A Turbines can interfere with electromagnetic telecommunications signals. A The presence of a telecommunications mast at a site or such signals which cross a site may therefore perplex the procedure of obtaining a edifice license. A A cheque for telecasting communications should besides be made which may non be evident from ocular review. Entree The distance to the nearest route entree and the complexness of the terrain will well act upon the capital cost of the undertaking. A Land handiness Land handiness varies from state to state but a possible site where there are comparatively few landholders and landholders who can give sole rights to the developer is the ideal state of affairs. The job of site happening lends itself good to a thorough and elaborate Geographical Information System ( GIS ) based attack where air current atlases, an electrical grid map, roads, environmental appellations and other standards can all be input and the optimum sites defined. A In pattern, nevertheless, a more matter-of-fact attack may good turn out more appropriate. 2. WIND FARM LAYOUT DESIGN The air current farm layout is typically designed utilizing a professional air current farm design bundle. A Such tools allows for an effectual loop and optimization of the cardinal parametric quantities for the layout. Preliminary layout design Once a site has been identified and the determination has been taken to put in its development the air current farm design process commences. A This is necessarily an iterative procedure. A The first undertaking is to specify the restraints on the development: Maximum installed capacity ( due to grid connexion or Power Purchase Agreement footings ) Site boundary Set dorsums from roads, homes, overhead lines, ownership boundaries etc. Environmental restraints Location of noise and shadow spark sensitive homes, if any, and appraisal standards Location of visually sensitive point of views, if any, and appraisal standards Turbine minimal spacings as defined by the turbine provider. Constraints associated with communications signals such as microwave nexus corridors, if any. Local ordinances that limit the turbine type permissible for the development. These restraints may alter as treatments and dialogues advancement with assorted parties. For the intent of specifying the preliminary layout it is necessary to specify about what sizes of turbine are under consideration for the development, as the installed capacity accomplishable with different sizes of turbine may change significantly. A The choice of a specific turbine theoretical account is frequently best left to the more elaborate design stage when the commercial footings of the assorted providers are known. Specification of anemometry The air current resource at the site is the cardinal parametric quantity in finding its economic viability. To measure the energy for a undertaking it is necessary to obtain informations on the local air current government. Typically this means installing anemometry equipment at the site. The preliminary layout allows the air current measurings to be made in appropriate locations. As a general regulation the mast should be at least two tierces of the hub tallness of the turbines. A utile regulation in complex terrain is that no turbine is located more than 1 kilometer from the closest mast. In really terrible terrain, the closest mast should be within 500m, but for air current farms located in simple terrain a much lower denseness of masts over the site may be appropriate. For big developments that require several masts there may be advantages in ab initio put ining merely one mast on the site. Once it is confirmed that the air current resource is sensible, other masts can be install ed to corroborate the fluctuation in air current velocity over the site country. Provided the original mast remains as a changeless mention other masts can be moved after, say, six months of operation to cut down the entire figure of masts required.+ Detailed layout design A cardinal component of the layout design is the minimal turbine spacing used. A In order to guarantee that the turbines are non being used outside their design conditions, the minimal acceptable turbine spacing should be obtained from the turbine provider and adhered to. The appropriate spacing for turbines is strongly dependent on the nature of the terrain and the air current rose at a site. A If turbines are spaced closer than 5 rotor diameters in a frequent air current way it is likely that intolerably high aftermath losingss will ensue. A For countries with preponderantly uni-directional air current roses, such as the San Gorgonio Pass in California, greater distances between turbines in the prevailing air current way and tighter spacings perpendicular to the prevailing air current way will turn out to be more productive. A Tight spacings require blessing by the turbine provider if warranty agreements are non to be affected. With the air current farm restraints defined, the layout of the air current farm can be optimised. A This procedure is besides called air current farm â€Å" micrositing † . A The purpose of such a procedure is to maximize the energy production of the air current farm whilst understating the substructure and operating costs and run intoing all restraints. A For most undertakings the economic sciences are well more sensitive to alterations in energy production than substructure costs. A It is hence appropriate to utilize the energy production as the dominant layout design parametric quantity. The elaborate design of the air current farm is facilitated by the usage of commercially available air current farm design tools. A Once an appropriate analysis of the air current government at the site has been undertaken, a theoretical account is set up which can be used to plan the layout, predict the energy production of the air current farm every bit good as being used to turn to economic and be aftering related issues. For big air current farms it is frequently hard to manually deduce the most productive layout. A For such sites a computational optimization utilizing a air current farm design tool may place a layout for which significant additions in predicted energy production are achieved. A Even a 1 % addition in energy production from improved micrositing could easy stand for an addition in one-year gross of $ 50,000 to $ 100,000 for a 50 MW air current farm. A The computational optimization procedure will normally affect many 1000s of loops and can include noise and ocular restraints. A Wind farm design tools handily allow many substitutions on air current farm size, turbine type, hub tallness and layout to be considered rapidly and expeditiously increasing the likeliness that an optimum undertaking consequences. A Financial theoretical accounts may be linked to the tool so that returns from different options can be straight calculated, further streamlining the development determination doing procedure. In many states the ocular influence of a air current farm on the landscape is an of import issue. A The usage of computational design tools allows the Zone of Visual Influence ( ZVI ) , or visibleness footmark, to be calculated to place from where the air current farm will be seeable. A The tools may besides be used to supply visual images, to ease the production of photomontages and to foretell the noise and shadow spark which consequences from a proposed development. A These are frequently cardinal facets of the Environmental Assessment for a undertaking. Figure 1 shows an initial preliminary layout of a air current farm consisting of 26 turbines that meets all site specific restraints. A There are two noise sensitive homes west of the proposed air current farm with a defined noise bound that are marked with brooding icons. A The solid black line represents the site boundary in which the turbines can be placed. The layout of the air current farm after the optimization is shown in Figure 2. A Compared with the initial layout the predicted energy production has increased by about 3 % . A In the upper subdivision of Figure 2 the optimised layout of the air current farm superimposed with the noise degrees predicted for this layout can be seen. A A rendered visual image of the air current farm visual aspect from a point of view sou’-east of the air current farm is shown at the underside. How to cite Site Finding And Planning For Wind Farms Environmental Sciences Essay, Essay examples

Langston Hughes Mother to Son free essay sample

This paper analyzes the content of the poem Mother to Son by the poet Langston Hughes. This paper examines the text of this poem from a African-American perspective. The analysis uses poetic devices and the background of the literary environment. Line by line analysis is provided to show how the poem uses the everyday ordinary dialect of blacks, and gives insight into the poverty and discrimination that blacks faced during the 1920s. `Between 1919 and 1926 there was a major population shift of African-Americans to the cities of New York, Chicago, and Washington, D.C (America Online). In 1921, Langston Hughes was one such African American who had traveled to New York to attend Columbia University. This population shift resulted in an obvious display of creativity among the African-American race. The creativity broadened the scope of African American influence on the American society, culture and primarily literature. The influence was so enormous and collective that it took form of a movement, which began in about 1920 and lasted until about 1930. We will write a custom essay sample on Langston Hughes Mother to Son or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page This period was first known as the `New Negro Movement,` but it later became known as the Harlem Renaissance. The Harlem Renaissance represented the African American intellect and the consequent intellectuals who celebrated their heritage and background with immense pride and gusto. It was during this movement and into this heady climate that the poem `Mother to Son` was introduced. The politico-literary climate was charged and just ripe and the need for African American contribution was being recognized. One of the critics voiced the urgent need when he cried, `what American literature decidedly needs at the moment is color, music, gust If the Negroes are not in a position to contribute these items, I do not know what Americans are.` `