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We say that a point estimator is unbiased if (choose one): Its sampling distribution is centered exactly at the parameter it estimates.
The director of security for an industrial site is thinking of closing one or more of the site's several gates to make it easier to control who gets in.
The main office of the franchise restaurant chain desires to be capable to predict what sales may be at proposed new locations for restaurants, based on what they've learned from their several hundr
A market research firm interviews travelers at LaGuardia airport to try to determine whether men or women would spend the most if the airport commission put in a new, upscale gift shop in the termin
Two independent random samples of size n1 = 24 and n2 = 20 are taken from the two normal populations. The sample means are x1-bar = 220 and x2-bar = 240. The variances are sigma1^2 = 15 and sigma2^2
Employ the survey result to give a 99% confidence interval for the mean study time of all first-year students:____±____(+-0.0001).
Assume that we know that the study time follows Normal distribution with standard deviation= 62.6328 minutes in population of all first-year students at this university. Employ the survey result to
A laboratory scale is known to have the standard deviation of 0.00094 grams in repeated weighings. Scale readings in repeated weighings are Normally distributed, with mean equal to true weight of th
Assume you choose a person at random. Supposing birthdays are uniformly distributed during the year, how likely is it that person will have his or her birthday upon a day of month that is divisible
Five hundred people are enrolled in the 10-year cohort study. At the start of study, 50 have diagnosed CVD. Over the course of study, 40 people who were free of CVD at baseline develop CVD. Determi
Two independent random samples of size n1 = 24 and n2 = 20 are taken from two normal populations. The sample means are x1-bar = 220 and x2-bar = 240. The variances are sigma1^2 = 15 and sigma2^2 = 1
A direct mail sales company should find its credit policies quite carefully. Assume that the firm suspects that advertisements in certain magazine have led to excessively high rate of write offs. Th
Tests on sample of 50 modified components produce mean time between failures of 740 hours. At the .01 level of significance, test the claim that modified components have a longer mean time between f
Determine the probability that among seven randomly chosen graduates, at least one finds the job in his or her chosen field in a year of graduating.
The annual snowfall in town has mean of 31 inches and standard deviation of 11 inches. Last year there were 67 inches of snow. How many standard deviations from mean is that?
A quiz consists of 70 multiple choice questions, each with the five possible answers, only one of which is correct. Determine the mean and the standard deviation of the number of correct answers.
A 28-year-old man pays $159 for one-year life insurance policy with coverage of $140,000. If the probability that he will live through the year is 0.9992, what is the expected value for the insuranc
You're dealt one card from 52 card deck. Then the card is replaced in deck, the deck is shuffled, and you draw again. Determine the probability of getting a picture card the first time and a heart t
Determine the minimum sample size you should use to assure that your estimate of will be within the required margin of error around the population p? Margin of error: 0.04; confidence level: 90%; fr
Discuss the meaning of the following percentiles: The 5th percentile of weight for three-year-old females is 11.66 kg and the 25th percentile of weight for three-year-old males is 13.38 kg.
A population is normally distributed with the standard deviation sigma = 349. We wish to test the hypotheses Ho: ? = 66,818; H1 = ? > 66,818. A 123-item sample has a mean = 66,399.2. Determine th
Do one of the following, as appropriate: Determine the critical value , find the critical value , or state that neither the normal nor the t distribution applies. 95% level of significance; n = 11;
Many firms use on-the-job training to teach their employees new software. Suppose you work in the personnel department of a firm that just finished training a group of its employees in new software
A study was designed to determine the effects of two variables (1) a student's level of mathematical anxiety and (2) teaching method on a student's achievement in a mathematics course.