Exam 7: Sampling and Sampling Distributions

The population of lengths of aluminum-coated steel sheets is normally distributed with a mean of 30.05 inches and a standard deviation of 0.3 inches.What is the probability that the average length of a steel sheet from a sample of 9 units is more than 29.95 inches long?

The internal auditing staff of a local manufacturing company performs a sample audit each quarter to estimate the proportion of accounts that are more than 90 days overdue (delinquent).The historical records of the company show that over the past 8 years,the average has been that 14 percent of the accounts have been delinquent.For this quarter,the auditing staff randomly selected 250 customer accounts.What are the mean and the standard deviation of the sampling distribution of ?

The population of all sample proportions has a normal distribution if the sample size (n)is sufficiently large.The rule of thumb for ensuring that n is sufficiently large is:

__________ sampling is defined as sampling where we know the chance that each element in the population will be included in the sample.

Selecting a random sample is the only way to ensure that the information reflects the true population.

A sample size of 500 is sufficiently large to conclude that the sampling distribution of is a normal distribution,when the estimate of the population proportion is .995.

If p = .8 and n = 50,then we can conclude that the sampling distribution of is approximately a normal distribution.

In systematic sampling,the first element is randomly selected from the first (N/n)elements.

The College Student Journal (December 1992)investigated differences in traditional and nontraditional students,where nontraditional students are defined as 25 years old or older and working.Based on the study results,we can assume the population mean and standard deviation for the GPA of nontraditional students is µ = 3.5 and σ = 0.5.Suppose a random sample of 100 nontraditional students is selected and the GPA for each student is calculated.Calculate

A low response rate has no effect on the validity of the findings from a survey.

As the sample size ___________,the standard deviation of the population of all sample proportions increases.

Find P( < 35)if μ = 40,σ_x = 16,n = 16.

An unbiased estimate of σ² is _____.

If the sampled population is exactly normally distributed,then the sampling distribution of is also expected to be normal,regardless of the sample size.

A random sample of size 36 is taken from a population with a mean of 50 and a standard deviation of 5.The sampling distribution of ____________________.

_____________ occurs when some population elements are excluded from the process of selecting the sample.

If the sampled population has a mean of 48 and standard deviation of 16,then the mean and the standard deviation for the sampling distribution of for n = 16 are:

The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches and a standard deviation of .08 inches.Suppose a random sample of 20 balls is selected.Calculate the mean of the sampling distribution of the sample mean.

_____________ is the difference between a numerical description of the population and the corresponding descriptor of the sample.

Find P( > 2,510)if μ = 2,500 and = 7.