9. The average amount you spend on a lunch during the week is not known. Based on past experience you are willing to assume that the standard deviation is $2.40. If you take a random sample of 36 lunches, what is the value of oz, the standard deviation of x? 10. According to one study, brain weights of men are normally distributed with a mean of 1.30 kg and a standard deviation of 0.13 kg. Determine the percentage of all samples of three men that have mean brain weights within 0.1 kg of the population mean brain weight of 1.30 kg. (Round answer to the nearest hundredth.) Page 2 of 3 RVCC Statistics I Homework 1 1. A teachers' association publishes data on salaries in the public school system annually. The mean annual salary of (public) classroom teachers is $54.7 thousand. Assume a standard deviation of $8.0 thousand. What is the probability that the sampling error made in estimating the population mean salary of all classroom teachers by the mean salary of a sample of 64 classroom teachers will be at most $1000? (Round answer to the nearest ten-thousandth, the fourth decimal place.) 12. A teachers' association publishes data on salaries in the public school system annually. The mean annual salary of (public) classroom teachers is $54.7 thousand. Assume a standard deviation of $8.0 thousand. What is the probability that the sampling error made in estimating the population mean salary of all classroom teachers by the mean salary of a sample of 256 classroom teachers will be at most $1000? (Round answer to the nearest ten-thousandth, the fourth decimal place.) 13. The scores on a university examination are normally distributed with a mean of 62 and a standard deviation of 11. What is the minimum mean of the exam that a random sample of 121 college students must score to be in the top 15% of similarly sized samples of college students? (Round answer to the hundredth.)