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Sampling

Sampling is utilized in statistics to survey a specific subset of a population as it is often not feasible to collect observations for an entire population. Sampling allows various descriptive statistical measures to be computed and these statistics are then useful in trying to estimate or infer the parameters for the entire population.

When conducting a statistical analysis, sampling basically simplifies the process. If a population contained 1 billion subjects, a researcher would be delusional to assume that all 1 billion individuals could be observed or surveyed. However, with sampling, a smaller portion of the individuals from that population could be analyzed. Then, through the use of inferential statistics, estimations could be made with regards to specific parameters applying to the entire population.

There are a multitude of different sampling techniques which can be employed when analyzing a population. Specifically, the most common sampling methods practiced are cluster sampling, systemic sampling, random sampling, nonprobability sampling, and stratified sampling. All of these sampling practices differ in terms of the criteria they use to collect samples and in certain situations one technique may be preferred over another.

In many cases, sampling needs to be implemented because it is impossible or too difficult to identify every unit in a population. Consider particular animal populations, such as sharks. It is not possible to count every shark residing in an ocean. Therefore, through sampling, statistical analyses can be done on populations of specific shark species and reasonable estimations can be construed regarding their total population size.

Clearly sampling is an integral part of any statistical study. However, sampling requires both resources and time, which are finite properties. Therefore, understanding the array of different sampling methods which are possible and when it is best to perform them is critical to efficient sampling in statistics.

Categories within Sampling

Cluster Sampling

Postings: 0

Cluster sampling is a specific type of sampling technique which is used on homogeneous populations and these target populations are divided into groups which are randomly sampled.

Systematic Sampling

Postings: 2

Systematic sampling is a form of random sampling in which units are selected in an ordered fashion according to a periodic interval, i.e. the 3rd or 5th person on every list is sampled.

Random Sampling

Postings: 30

Random sampling is when every single element in an entire population has an equal probability of being selected.

Nonprobability Sampling

Postings: 2

Nonprobability sampling is not based on the probability theory because elements are not randomly selected and it is a technique often used for qualitative research.

Stratified Sampling

Postings: 1

Stratified sampling is a method in which a population is divided into separate groups, called strata, based upon specific characteristics such as gender or age.

Exploratory Analysis of Quantifiable Variables

Using information from Page 5- 15: What are the four purposes of this chapter: (1) describe the research methodology of this study, (2) explain the sample selection, (3) describe the procedure used in designing the instrument and collecting the data, and (4) provide an explanation of the statistical procedures used to analyze t

Clustered and stratified sampling

A. Design effects are used to evaluate the precision of statistics for different sample design. Is the design effect of a clustered element sample likely to be larger or smaller than one? Is the design effect of a stratified element sample likely to be larger or smaller than one? In a single stage clustered sample, if within

Collecting Data from a Telephone Survey

A person decides to take a telephone survey of 40 families in the 721-exchange area (sometimes referred to as prefix). You want an excellent representation of all subscribers in the exchange area. Explain how you will carry out this study.

Statistical Data Measures

Classify each of the following as nominal, ordinal, interval or ratio data: a) The time required to produce each tire on an assembly line. b) The number of quarts of milk a family drinks in a month. c) The ranking of four machines in your plant after they have been designated as excellent, good, satisfactory, and poor. d)

Listing sample sizes and computing the mean of a sample

A population consists of the following five values: 11, 12, 14, 15, and 17. a. List all samples of size 3, and compute the mean of each sample (Round your Mean value to 2 decimal places) b. Compute the mean of the distribution of sample means and the population mean (Round your answers to 2 decimal places)

Western Electric runs rule

See attached for data. 1. A Lean Six Sigma black belt project results in a lower defective rate at the final inspection of a plastic molded component. Thirty days of data presented in the following table. (a) Create the appropriate control chart for the improved process. Apply only Western Electric runs rule 1 for deter

Sampling Distribution of Sample Mean: Price of Home

The average price of a home is reported to be $203,190. Use this price as the population mean, and assume the population standard deviation is 43,890. What is the probability that the mean price for a sample of 18 homes is within 14,250 of the population mean?

Machine Learning Question

I have been giving the following problem in machine learning which I am new to. Is there a specific concept that this problem is testing; so maybe I can do some reading/research on it and try applying those principles to the problem? Thanks for any help/hints/direction. You are a visiting Professor in the first and only Unive

Choosing the Right Sampling Designs

I'm practicing on choosing the right sampling designs. I have come up with answers below but I do not think they are correct. Please, verify and provide the correct answer with explanations. What kinds of sampling designs would be used for the following? a. A study to get a quick idea of the medical acceptability of a ne

Identifying Types of Samples

1. 49, 34, and 48 students are selected from the Sophomore, Junior, and Senior classes with 496, 348, and 481 students respectively. Identify which type of sampling is used and why. 2. The name of each contestant is written on a separate card, the cards are placed in a bag, and three names are picked from the bag. Identify wh

Statistics Problem Set: Independent and Dependent Variables

1. The Chicago Tribune of July 21, 1995 reported on a study by a fourth-grade student named Beth Peres. In the process of collecting evidence in support of her campaign for a higher allowance, she polled her classmates on what they received as an allowance. She was surprised to discover that the 11 girls who responded reported a

Mean of Sampling Distribution

The assets (in billions of dollars) of the four wealthiest people in a particular country are 47,35,28,11. Assume that the sample of size 2 are randomly selected with replacement from this population of four values. a) After listing the possible samples and finding the mean of each sample, use the table to describe the sampli

Flexible Working Schedule for Women with Children

Companies often make flextime scheduling available to help recruit and keep women employees who have children at home. Other workers sometimes view these flextime schedules as unfair. An article in Nikkei Article indicated that 5% of male employees state that they have to pick up the slack for moms working flextime schedules. Su

Sampling: Lower and Upper Control Limits

Random samples of five hundred units that were selected daily from a manufacturing process produced an overall defective rate of 3.5%. Calculate the lower and upper control limits for a percentage control chart.

Statistics: Sample Pulse Rates of Men and Women

A sample of pulse rates of men and women are used to construct a 95% confidence interval for the difference between the two population means, and the result is -12.2 < u1 - u2 < -1.6, where pulse rates of men correspond to population 1 and pulse rates of women correspond to population 2. Express the confidence interval with puls

Statistics: Sampling Distribution of Tire Life Span

A manufacturer claims that the life span of its tires is 52,000 miles. You work for a consumer protection agency and you are testing these tires. Assume the life spans of the tires are normally distributed. You select 100 tires at random and test them. The mean life span is 51,853 miles. Assume = 700. Assuming the manufactur

Identifying Sampling Types

The personnel manager at a company wants to investigate job satisfaction among the female employees. One evening after a meeting, she talks to all 30 female employees who attended the meeting. Does this sampling plan result in a random sample? Simple random sample? Explain.

Selecting Appropriate Survey Techniques

The human resources (HR) manager for Gargantua, Incorporated wants to give a short survey to a sample of recent hires (defined as people who have been with the company for less than one year). This sample will include several thousand individuals. The HR manager wants to be able to develop a confidence interval for the proportio

What sample size is necessary for a study

Problem is: What sample size is ncessary for a study to determine the average cost of a child delivered at a local hopsital within the past 3 months? (I have determined a sample size of 1,300. I came up with this number because there are 10,416 births a year in Louisville, KY where the basis of this problem is. 10,416 / 12 m

Applied statistics in nursing

Explain the importance of random sampling. What problems/limitations could prevent a truly random sampling and how can such problems be avoided?

Sampling in business

Why is sampling important to business? Are there situations in business where sampling would not be effective?

Statistics Problems

The branch manager of a pet supply store wants to study characteristics of customers of his store. In particular, he decides to focus on two variables: the amount of money spent by customers and whether the customers own only one cat. 1. If he wants to have 95% confidence of estimating the true population mean amount spent in

Population or Sample

1) Determine whether the evaluated group is a population or a sample a) Based on a randomly selected group of 500 patients with high cholesterol, it was found that 67% have heart disease. Is this a population or a sample; explain your answer. b) An investigation of 150 randomly selected local restaurants concluded that 42%

Sampling Distribution of a Sample Mean: University Tuition

According to the College Board's report, the average tuition and fees at four year private colleges and universities in the United States was $18,273 for the academic year 2002 - 2003 and the standard deviation was $2100. For a random sample of 100 four year private U.S. colleges, answer the following: a. What is the mean of

Simple confidence interval and approximations

Suppose that in a population of 10 items, 3 are defective and 7 are not. Suppose that two items are chosen at random for inspection. Let X be the number of defective items inspected. report all probabilities to a minimum of 5 decimal places of accuracy. (a) Clearly explain why X does not have a binomial distribution. [Hint: W

Calculations for sampling distribution of sample mean

For one quantitative coures in a college with 10,000 students, it is calculated that students test scores are normally distributed with a mean of 80 and a standard deviateion of 16. Assume now we randomly select a sample of 64 students test scores. a.) What is the probability that the average test score of the sample selecte

I am not sure where to begin with the part b?

Credit card companies frequently use statistics to monitor their customerââ?¬â?¢s accounts for fraudulent activities. If any ââ?¬Å"unusualââ?¬Â? activity is noticed, the customer is contacted to make sure that the credit card has not been compromised. Listed below are the daily charges on a specific customerââ?¬

Sampling distribution of sample proportion

Last year, a national opinion poll found that 43% of all Americans agree that parents should be given vouchers good for education at any public or private school of their choice. Assume that in fact the population proportion is 0.43. A random sample of 350 is to be selected and asked the same question. a) What is the shape, m