Question

(1) A survey found that the American family generates an average of 17.2 pounds of glass garbage each year. Assume that standard deviation of the distribution is 2.5 pounds. Find the probability that the mean of a sample of 55 families will be between more than 18 pounds. Assume that the sample is taken from a population normally distributed. (2) The average weight of 40 randomly selected minivans was 4150 pounds. The population standard deviation was 480. Find the 99% confidence interval of the true mean weight of all minivans. (3) The sample of 8 social networking sites has a mean of 13.1 millions of visitors for a specific month. The standard deviation was 4.1 million. Find the 95% confidence interval of the true population mean. ( Use t-scores ) (4) A biologist know that the probability is only 0.65 that any given Arctic tern will survive the migration from its summer nesting area to its winter feeding grounds. A random sample of 500 Arctic terns were banded at their summer area. Use the normal approximation to the binomial and the probability that between 310 and 340 of the banded arctic terns will survive the migration. (5) Seth wants to estimate the proportion of people in large metropolitan area who do at least 2 hours of volunteer work per week. A random sample of 60 people showed 28 of them did at least 2 hours of volunteer work per week. How large a sample does he need to say with 95% confidence that the error in his estimate is no more than 0.02 ?

Answer 1

Answer: