BIO 124 LAB ESTIMATING POPULATON SIZE 2. ESTIMATE oF THE SIZE OF THE HoMELEss UN
ID: 3178311 • Letter: B
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BIO 124 LAB ESTIMATING POPULATON SIZE 2. ESTIMATE oF THE SIZE OF THE HoMELEss UNAccoMPANIED YouTH POPULATION IN METRO ATLANTA One of the main goals of any survey sampling technique be able to generalize survey findings t larger population, or universe, of individuals. Traditional random sampling methods are ideal, but they require a sampling frame where all individuals in the universe have a known probability of being included inthesample, the example of alarge survey by a homeowners' association: the universe of potential survey respondents is known hera"" ers in the neighborhood are required to belong to the association, anu unerenoreuninnauntea houses are also easily identified. A simple random selection method-such as administering the survey at every fifth inhabited home on each streetin the neighborhood- would yield a survey dataset that is generalizable to the universe of all homeowners in the neighborhood. In hidden and hard-to-reach survey populations, however, we rarely know the probability that any individual will be included in the study through a given sampling design. We do not know the size of the universe (ie., the list of inhabited home addresses) nor the probablity that any individual from the universe would be sampled using a "random" selection method (ie, we cannot selecteveryfifth individual since we do not know each individual's location). For hidden or hard-to-reach populations researchers must use more sophisticated sampling methods the goal is for the survey results to be generalized to the larger (yet hidden and unknown) universe. capture-recapture, on the other hand, is not based on the social networks of prospective participants at all, First developed for estimating animal wildlife populations, capture-recapture allows researchers to estimate the size of universe based on whether a member of auniverse has been sampled once, multiple times, or not at all over the course of an extended period of research observation (Darroch & 1980; Seber, 1982, 1986, 1992) These observational data are used to estimate the size of the unknown universe based solely on probabilities calculated from the number of members observed-or "captured either once or multiple times during the observation period. Teams visited each location multiple times and at different times of day and night during the study.Each youth encountered was asked to complete a 10-15 minute survey about their current and past experiences with homelessness, including questions about common factors that canlead to youth homelessness. The survey also asked about their personal and family background, health status, and contact with health and outreach organizations. All surveys were conducted completely anonymousy in order to encourage honesty and protect respondents from any harm or negative consequences stemming from their answers. No information was collected that couldbe used to identify or troce participants. Upon completion of the survey, respondents received a$10 Visa card and a list of useful resources available to them in the community. Exert from the 2015 assessment of homeless youth numbers and needs in Atlanta, GA Wright, ER al 2015Aaansa Your Final Rupert stimate of the number of homeless youth in Atlanta, GA was undertaken using capture-reExplanation / Answer
Answer:
Difficulties that investigators encountered in estimating the size of the homeless youth population in Atlanta: The specific challenge in this case was the hard to reach or hidden population of homeless youth in Atlanta for survey data collection. In such cases it is difficult to perform survey sampling using standard probabiltiy methods
b) Factors that might violate the assumptions of mark recapture methods for estimating population size.Example of assumption of the Lincoln Peterson method this study violates and how the results of the homeless youth count would be affected by this violation:
In mark and recapture method, a number of individuals in a natural population are first marked and then returned to the population, some of these individuals are then subsequently recaptured to serve as a basis for estimating the size of the population.
Factors that might violate mark and recapture method assumptions: One critical assumption in mark and recapture technique is that the proportions should remain constant during the interval between the preliminary marking period and the subsequent recapture period. That is the population more or less should have remained the same (closed) - there is no addition to the population by means of new birth, immigration etc.
Another important factor is the length of the sampling period. A shorter time interval between marking and recapturing reduces the chance of violation of assumption. if the time duration is more then the chances of any alteration in population size increases which may violate the assumption.
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