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The sample size is n = 100. What are the expected value and the variance of the sample mean ?
You want the standard deviation of the sample mean to be at most 25. What is the minimum sample size you should use?
When sampling is for a population proportion from a population with actual proportion p = 0.5, using a sample of size n = 120.
If you can take the deviations of these data from any number you select, and you want to minimize the sum of the squared deviations (SSD).
Your bank sends you a summary statement, giving the average amount of all checks you wrote during the month.
You are allowed to take the deviations of the data points in a sample of size n, from k numbers you select, in order to calculate the sum of squared deviations.
An advertisement for Citicorp Insurance Services, Inc., claims “one person in seven will be hospitalized this year.”
Shimano mountain bikes are displayed in chic clothing boutiques in Milan, Italy, and the average price for the bike in the city is $700.
A quality-control analyst wants to estimate the proportion of imperfect jeans in a large warehouse. The analyst plans to select a random sample of 500 pairs.
Suppose that you have two statistics A and B as possible estimators of the same population parameter.
Suppose that in a sampling survey to estimate the population variance, the biased estimator (with n instead of n 1 in the denominator of equation 1–3).
Estimator A has a bias equal to 1/n (that is, the mean of the estimator is 1/n unit away from the parameter it estimates).
Three random samples of sizes, 30, 48, and 32, respectively, are collected, and the three sample means are computed.
f the university wants only the top 75% of the students to be eligible to apply, what should be the minimum GMAT score specified for eligibility?
If the project duration exceeds 250 days, a penalty will be assessed. What is the probability that the project will be completed within 250 days?
The profit (or loss) from an investment is normally distributed with a mean of $11,200 and a standard deviation of $8,250.
What are the mean and standard deviation of the total revenue on a particular day? Will the total revenue on a day be normally distributed?
Discuss the concepts of a parameter, a sample statistic, an estimator, and an estimate. What are the relations among these entities?
Thirty-year fixed mortgage rates in April 2007 seemed normally distributed with mean 6.17%.14 The standard deviation is believed to be 0.25%.
Compute an estimate of the mean amount of all accounts receivable. Give an estimate of the variance of all the amounts.
An article in the New York Times describes an interesting business phenomenon. The owners of small businesses tend to pay themselves.
Starbucks regularly introduces new coffee drinks and attempts to evaluate how these drinks fare by estimating the price its franchises can charge.
A market research worker interviewed a random sample of 18 people about their use of a certain product.
The number of newspapers demanded daily in a large metropolitan area is believed to be an approximately normally distributed random variable.