Explore BrainMass
Share

Sampling

Sampling in statistics

What is the purpose of sampling? What are some concerns and dangers of sampling? How important is the sample design to data validity? Explain. Provide an example where a sample might misrepresent data validity.

expected proportion of the sampling region

Suppose the porportion X of surface area in a randomly selected quadrate that is covered by a certain plant has a standard beta ditribution with alpha = 5 and beta = 2 a) Compute E(X) and V (X) b) Compute p(X <= 0.2) c) Compute P( 0.2 <= X <= 0.4) d What is the expected proportion of the sampling region covered by the plant?

Estimate the mean total cholesterol levels of children 2 - 6 years of age

A study is run to estimate the mean total cholesterol level in children 2- 6 years of age. A sample of 9 participants is selected and their total cholesterol levels are measures as follows: 185,180,225,240,194,147,196,175 and 223. a. Compute the sample mean b. Compute the sample standard deviation c. Compute the median d.

Non Probability Sampling

Your task is to complete a representative sample of attendees for the large concert Venue. The new season schedule includes 200 live concerts featuring all types of musicians and musical groups. Since neither the number of attendees nor their descriptive characteristics are known in advance You decide on non probabili

Compute Sample Size for Mean and Proportion: Example Problem

Suppose you want to use a simple random sample to determine, within +/- \$10 and at a 95% level of confidence, the average amount of money an OSU undergraduate student spends on text books in a semester. If you know that σ = 60, compute the sample size you need. There are 50,000 households in a city. You want to use a simpl

Sampling error be completely eliminated by taking larger sample sizes

Can a sampling error be completely eliminated by taking larger sample sizes?

Nonprobability Sample Data

Your task is to interview a representative sample of attendees for the large concert venue where you work. The new season includes 200 live concerts featuring all types of musicians and musical groups. Since neither the number of attendees nor their descriptive characteristics are known in advance, you decide on a nonprobability

Statistics sampling methods: Independent, dependent, and matched pair samples

1. Determine whether the sampling method is independent or dependent for the following example. A researcher wants to know whether the newly issued "state" quarters have a mean weight that is different from "traditional" quarters. He randomly selects 18 "state" quarters and 16 "traditional" quarters. Their weights are compared.

Sampling Distribution for Process Repeated

Consider the process of repeatedly taking SRSs of size n from a heavily left--&#8208;skewed population distribution with mean &#956; and standard deviation &#61683;&#61472;and calculating the sample mean x (a) What is the mean of the sampling distribution of x (b) What is the standard deviation of the sampling distribution of

Sampling distribution of the Mean for Ping-Pong balls

The diameter of Ping-Pong balls manufactured at a large factory is approximately normally distributed, with a mean of 1.30 inches and a standard deviation of 0.04 inch. If you slect a random sample of 16 Ping-Pong balls, a) What is the sampling distribution of the mean? b) What is the probability that the sample mean is les

Statistics multiple choice: sampling methods, coverage error, statistical inference

1) What is the difference between probability sampling and simple random sampling? A. There is no difference. B. Simple random sampling is a type of probability sampling. C. Probability sampling is a type of simple random sample. D. In probability sampling each item has an identical chance of being chosen. 2

P-Value and Interpretation of Meaning

The owner of a supply store needs to know if the mean amount of turpentine in 1- gallon containers bought from a well known company is indeed 1 gallon. Knowing that the standard deviation for the amount of turpentine is 0.02 gallon, he selects a random sample of 50 containers, and the mean amount of turpentine per 1-gallon cont

Independent or Dependent Samples

1. Classify as independent or dependent samples: White blood cell counts for a group of volunteers before being innoculated, and white blood cell counts for a second group of volunteers after being innoculated. 2. Classify as independent or dependent samples: White blood cell counts for a group of volunteers before being inno

Statistics : Proportionate stratified sample

You wish to do a community needs assessment survey of a community to find out how much office space is needed by professionals in the community. To do this you will select a proportionate stratified sample of professional . The population consists of 75 dentists 175 physicians 250 lawyers 25 psychiatrists 25 misc. Assu

Finding value of the sample test statistic

The dean of a nursing school claims that the average starting salary of its graduates is more than 60 (in \$000's). It is known that the population standard deviation is 10 (in \$000's). Sample data on the starting salaries of 64 randomly selected recent graduates yielded a mean of 62 (in \$000s). What is the value of the sample te

Statistics: Sample mean of breaking strength for trash bag manufacturer

Recall that the trash bag manufacturer has concluded that its new 30 gallon bag will be the strongest such bag on the market if its mean breaking strength is at least 50 pounds. In order to provide statistical evidence that the mean breaking strength of the new bag is at least 50 pounds, the manufacturer randomly selects a sampl

The Electronics Associates Sampling Problem: Plot the distribution and record statistics

See attached file. The director of personnel for Electronic Associates, Inc. (EAI),has been assigned the task of developing a profile of the company's 2500 managers. The characteristics to be identified include the mean annual salary for the managers and the proportion of managers having completed the company's management tra

Statistics - Do free Samples work?

Free Samples use the graph, which shows what adults think about the effectiveness of free samples. 15. Do Free Samples Work? You interview a random sample of 50 adults. The results of the survey show that 48% of the adults said they were more likely to buy a product when there are free samples.At can you reject the cla

Question: A SAMPLE HAS ss = 20 AND S^2=4 (TO THE POWER OF 2=4) . HOW MANY SCORES ARE IN THE SAMPLE? 1. 5 2. CANNOT BE DETERMINED WITHOUT ADDITIONAL INFORMATION 3. 6 4. 4 MULTIPLE CHOICE QUESTION.

Statistics - Simple Random Sampling & Cluster Sampling

Compare the differences of simple random sampling and cluster sampling using specific examples, and show the advantages and disadvantages of each method. What are the advantages and disadvantages of systemic random sampling and stratified random sampling?

Occupational Group for Alcoholism

A state magazine once published a story saying that farmers lead other groups in the consumption of alcohol. As evidence, it pointed to the fact that a rehabilitation center located in the rural part of the state treated more farmers than any other occupational group for alcoholism. Do you agree? Why or why not? Justify your

Sampling Methods: Example Questions

The average American male wears a size 10 shoe and spends 4 hours a year tying a tie. The average American female college student owns 3.5 pairs of jeans. The average American laughs 15 times daily, swallows 215 aspirin tablets a year, and has a dog weighing 32 pounds. a. Choose one of these estimates. How do you suppose it

Statistics

Please see attached for the full details of the problem. 1. (2 pts) The objective of statistics is best described as: A) To make inferences about a sample based on information we get from a population B) To make inferences about a population based on information we get from a sample taken from the population C) To use p

Examining the Confidence Intervals for Two Populations

Consider the result in the following table for two random sample taken from two populations: Sample 1 n1 = 50 - x = 22 σ1 = 4 Sample 2 n2=35 - x2 = 14 σ2= 5 a) provide a 90% confidence interval for difference between the two population means. b) provide a 97% confidence interval for the difference

Identifying Sample and Populations

Identify the sample and population 1. a. A group of 50,000 randomly selected college students were surveyed about whether they have a TV in their dorm room. Only 75% said yes to the question. i. Sample - ii. Population - b. An employee at the local ice cream emporium asks 3 customers if they liked cookie dough ice

Sample Distribution for Work Processing Formulas

I need to word-process the formulas using the Equation function in MS Word(not using Excel). Time lost due to employee absenteeism is an important problem for many companies. The human resources department of Western Electronics has studied the distribution of time lost due to absenteeism by individual employees. During a on

Sampling Distribution of the Mean - Library

A library checks out an average of 250 books per day, with a standard deviation of 75 books. If a sample of 36 days of operation is selected and the sample mean is computed, a. What is the expected value of the sample mean? b. What is the value for the standard error of the mean? c. What is the probability that

Sampling and Sampling Distribution-3 questions

1. Suppose you need to sample the concentration of a chemical in a production process that goes on continuously 24 hours per day, 7 days per week. You need to generate a random sample of six observations of the process over a period of one week. Use a computer, a calculator, or a random number table to generate the six observa

sampling methods statistics

Each new employee of a department store is given an identification. The personnel records are sorted in sequence starting with employee number 0001. To probe the employees regarding their work shift, the first elected 0153. The numbers 0253, 0353, 0453, were chosen so forth, become members of the sample. This type of sampling is

Solving a sample size calculation problem

How does the bell-shaped curve for the sampling distribution of sample means for samples of size n = 120 compare to the bell-shaped curve for the sampling distribution of sample means for samples of size n = 95? Answer: A curve with a sample size of 120 will fit a perfect curve more accurately than a curve with a sample size