For each of the scenarios below, determine if the sample is a simple random samp
ID: 3340896 • Letter: F
Question
For each of the scenarios below, determine if the sample is a simple random sample from the population
of interest, or if the sample has some form of bias. If there is a bias, describe the nature of the bias in a
sentence or two.
(a) You are interested in the average height of all freshmen on a college campus. You draw a
simple random sample of freshmen in your statistics class.
(b) You are interested in the range of the glaze thicknesses on mugs created in a factory. You sample every
5th mug o of the assembly line.
(c) You are interested in the average IQ of 6th graders in Daze County public schools. You get your sample
by using computer software to randomly select 100 6th grade student ID numbers from the Daze County
public school database.
(d) You work for a doctor's office and you are interested in estimating the proportion of patients that visited
the office in the last month that feel they received satisfactory care. You randomly select names from
the list of patients who have been to the office, and email them a survey. About 25% of the surveys are
returned.
Explanation / Answer
a) Yes, simple random
Although simple random sampling is intended to be an unbiased approach to surveying, sample selection bias can occur. When a sample set of the larger population is not inclusive enough, representation of the full population is skewed and requires additional sampling techniques.
b) This is systematic sampling
The aim of the systemic random sample is to reduce the potential for human bias in the selection of cases to be included in the sample. As a result, the systemic random sample provides us with a sample that is highly representative of the population being studied, assuming that there is limited missing data.
The advantage of systematic sample is that it really fast and easy to convenient when you already have a list of the units in your population. But the disadvantage is that systematic sample might lead to bias. Suppose the population is arranged in a pattern and if the periodicity of sampling might exactly match the periodicity of that pattern.
c) In practice, the lottery method of selecting a random sample can be quite burdensome if done by hand. Typically, the population being studied is large and choosing a random sample by hand would be very time-consuming. Instead, there are several computer programs that can assign numbers and select n random numbers quickly and easily.
Limited bias or no bias as it is done by computer
d) A voluntary sample is one of the main types of non-probability sampling methods. A voluntary sample is made up of people who self-select into the survey. Often, these folks have a strong interest in the main topic of the survey. Suppose, for example, that a news show asks viewers to participate in an on-line poll.
Voluntary Response Bias. In survey sampling, voluntary response bias occurs when sample members are self-selected volunteers, as in voluntary samples . An example would be call-in radio shows that solicit audience participation in surveys on controversial topics (abortion, affirmative action, gun control, etc.).
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