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# Sampling

### What is a sampling error? Reasons to use sampling?

1.) a.) What is sampling error? Could the value of the sampling error be zero? If it were zero, what would this mean? b.) List the reasons for sampling. Give an example of each reason for sampling.

### Distribution of Sample Mean: Breaking strength of steel cable

The breaking strength of a certain brand of steel cable is normally distributed, with a mean of µ = 2500 pounds, and a standard deviation of Ï? = 250 pounds. If a construction company buys 25 cables, what is the probability that they will have a mean breaking strength of at least 2400 pounds? Express your answer as a d

### Sample size for estimating population mean

The manager of a paint supply store wants to estimate the actual amount of paint contained in 1 gallon cans purchased from a nationally known manufacturer. The manufacturer's specifications state that the standard deviation of the amount of paint is equal to 0.02 gallons. A random sample of 50 cans is selected, and the sample

### Infomercials Products

Infomercials often peddle products under the guise of "studies show". While some of the products are surprisingly good (e.g., FoodSaver, Foreman Grill, Ronco Rotisserie), many of the products are not. a. Why should you be initially suspicious of any products advertised on these shows, despite the "existence" of data? b. What

### Population Parameter and Sample Estimate

You have been told that for university classes, students are supposed to spend two hours working outside of class for each hour in class. You are curious to know the average amount of time students at your school spend working outside of class for each hour in class. You contact 100 students at your school and ask them, 'How ma

### Random Sampling for proportion of population

5. The manager of University Credit Union (UCU) is concerned about checking account transaction discrepancies. Customers are bringing transaction errors to the attention of the bankâ??s staff several months after they occur. The manager would like to know what proportion of his customers balance their checki

### Statistics: Identification of Sampling Method and Analysis

1. Five early adolescents in each program participated in the study. The young people ranged in age from 11 to 13 years and all were racial minorities. The three boys in the Manhattan neighborhood were of Hispanic/Latino origin and the two girls were African American. Conversely, the four boys in the Bronx neighborhood were Afr

### Accurate samples and unbiased results

How can we be certain that surveys and statistics that we hear about in the media are accurate samples and unbiased? Is there a way to dissect the information and determine if a probability sample was used?

### Curve the sample of scores assuming grades are normally

Consider this a sample of scores and let's curve these grades using the following approach: Grades: 82,99,76,87,80,76,91,97,74,72,47,95,87,51,82,104,66,20,65,96,71,82,92,90,98, 68,67,83,94,98,74,84,90,35,92,101,77,96,100,49,98,82,105,104 1- Assume these grades are normally distributed 2- Give a C to the students in the

### Statistics: Sampling and Sampling Distributions

1.) Suppose a simple random sample of size 50 from a population with a mean of 10. Find the value of the standard error of the mean in each of the following cases (use the finite population correction factor if appropriate.) a.) the population size is infinite b.) the population size is N=50,000 c.) the population size is N

### Statisitics: What is the purpose of sampling? What are dangers of sampling?

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

### Independence assumption of samples is violated; proportion, percentage and ratio

Question 1: When a researcher has two samples with two means, one of the assumptions for two samples is independence of between the two samples. What does this mean? What happens if the independence assumption is violated? Questions 2: What are the differences among a proportion, a percentage, and a ratio? When would

### Sampling from a population.

The file HP.xls contains the ages of 48 moviegoers to a recent showing of a Harry Potter movie.The following two methods illustrate in different ways how you might select a random sample of eight moviegoers' ages. In each case use the initial order of the files ages as the starting point, so that the first person in the list is

### Levels of significance for calls in response to state of the union address

The response to the President's state-of-the-nation address was overwhelmingly positive. The White House switchboard received 1532 calls supporting his views and only 122 that were opposed. Comment on this situation and the results.

### Sample size for mean and Proportion

A consumer agency has retained an independent testing firm to examine a television manufacturer's claim that its 25-inch console model consumes just 110 watts of electricity. Based on a preliminary study, the population standard deviation has been estimated as 11.2 watts for these sets. In undertaking a larger

### 8.25 Error of the Sample Proportion for female purchasing managers

SEE ATTACHED FILE - Error of the Sample Proportion It has been reported that 42.6% of U.S. workers employed as purchasing managers are females. In a simple random sample of U.S. purchasing managers, 70 out of the 200 are females. Given this information: a. What is the population proportion, &#960;? b. What is the sample

### Memo to Universal Credit for sampling to meet requirement

A partner company to American Intellectual Union (AIU), Universal Credit Inc., would like to examine the required sample size needed to be able to estimate the mean dollars that each card holder will spend each month. It would like to be within plus or minus \$10 of the true mean with a 98% confidence level. The standard deviatio

### Independent variable for ballet training of baseball team

A coach in a large high school thinks that ballet training will improve the batting performance of his baseball team. He decides to have a randomly selected half of the team take six weeks of ballet training before the baseball season begins, while the other half does not take such training. He will then compare the season bat

### Two independent samples

Why is it important that two samples be independent? Explain.

### Statistics and Sampling: Example Problem

Assume we have three different samples each comprised of 20 different jurisdications. Our objective is to compare the seriousness of juvenile substance abuse across all the samples. Sample 1 has en average of 1862 arrests of youth substance abuse; Sample 2 has an average of 3965 and Sample 3 has an average of 2398 arrests. W

### T Tests for Independent and Related Samples: 6 problems

See attached file for clarity. t Tests for Independent and Related Samples Problem Set 2: Chapter 10 & 11: problems: Chapter 10: 2. Describe what is measured by the estimated standard error in the bottom of the independent -measures t-statistic. 18. In 1974, Lotus and Palmer conducted a classic study demonstrat

### Survey of doctors involved in malpractice suits in last 3 years

An insurance company wants to know the proportion of medical doctors in New York involved in at least one malpractice suit in the last three years. They survey a random sample of 200 medical doctors in New York. a. What is the population? b. What is the sample? c. Could the insurance company generalize and say that this

### Analyzing data involving sex distribution, age, ethnicity

(1) Determine 10 variables of interest and determine the appropriate scale of measurement for each variable using the excel sheet attached. (2) Choose and compute the appropriate descriptive statistics to describe characteristics of the sample under study (such as sex distribution, age, and ethnicity) and the anxiety reported

### Sampling distribution of sample mean..

In the article "Job Mobility and Wage Growth" (Monthly Labor Review, Vol. 128, No. 2, pp 33-39), A. Light examines data on employment and answers questions regarding why workers separate from their employers. According to the article, the standard deviation of the lengths of time that women with one job are employed during the

### distribution of sample means, deviation, sample size, random selection

2. Describe the distribution of sample means (shape, expected value, standard error) for samples n= 36 selected from a population with a mean of µ =100 and a standard deviation of Ï? = 12. 6. For a population with a mean of µ =50 and a standard deviation of Ï? = 10, how large a sample mean (M) and the population mean for

### Statistics: Analyze and chart data from AIU job satisfaction sampling

See attached files for data and chart. Using our data set from Unit 1, compose an email to the head of the American Intellectual Union which discusses the following: Begin your email to AIU by first providing an overview of the database, i.e. a story about the characteristics which may include the types of variables inclu

### Differences in dependent and independent samples; relationship between variables

What are differences between dependent and independent samples? Provide examples. What are the implications for determining the tests used to analyze data? Discuss the relationship between independent and dependent variables with regard to correlation and regression analysis. What is the purpose of these terms?

### Random sample of 10 found that 9 were pro-life. Significance of a larger sample.

If a random sample of 10 people found that 9 were pro-life (i.e., 90%), while another random sample of 1,000 people from the same population found that 550 were pro-life (i.e., 55%), which would you find more significant? Why?

### 6-7: Sample size for candidate preference with 90% confidence level

A pollster for a congressional candidate would like to determine the proportion of the voting population who prefers this candidate at this time over the competition. He would like to estimate with .05 of the true proportion with a confidence level of 90%. What is the sample size needed? a) 171 b) 271 c) 298 (See the atta

### Discussing Sampling: Importance, Challenges, and Validity

Question: 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.