28. [-/4 Points] DETAILS MY NOTES ASK YOUR TEACHER Coal is carried from a mine in West Virginia to a power plant in New York in hopper cars on a long train. The automatic hopper car loader is set to put 68 tons of coal into each car. The actual weights of coal loaded into each car are normally distributed, with mean / = 68 tons and standard deviation o = 1.5 ton. In USE SALT (a) What is the probability that one car chosen at random will have less than 67.5 tons of coal? (Round your answer to four decimal places.) (b) What is the probability that 28 cars chosen at random will have a mean load weight x of less than 67.5 tons of coal? (Round your answer to four decimal places.) (c) Suppose the weight of coal in one car was less than 67.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment? Yes O No Suppose the weight of coal in 28 cars selected at random had an average x of less than 67.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment? Why? Yes, the probability that this deviation is random is very small. Yes, the probability that this deviation is random is very large. No, the probability that this deviation is random is very small. O No, the probability that this deviation is random is very large.29. [-/5 Points] DETAILS MY NOTES ASK YOUR TEACHER Over the past several months, an adult patient has been treated for tetany (severe muscle spasms). This condition is associated with an average total calcium level below 6 mg/dl. Recently, the patient's total calcium tests gave the following readings (in mg/dl). Assume that the population of x values has an approximately normal distribution. 9.4 8.5 10.9 8.9 9.2 9.1 10.6 9.2 11.5 12.4 USE SALT (a) Find the sample mean reading x and the sample standard deviation s. (Round your answers to four decimal places.) X = mg/dl S mg/dl (b) Find a 99.2% confidence interval for the population mean of total calcium in this patient's blood. (Round your answer to two decimal places.) lower limit mg/dl upper limit mg/dl (c) Based on your results in part (b), do you think this patient still has a calcium deficiency? Explain. Yes. This confidence interval suggests that the patient may still have a calcium deficiency. Yes. This confidence interval suggests that the patient no longer has a calcium deficiency. O No. This confidence interval suggests that the patient may still have a calcium deficiency. No. This confidence interval suggests that the patient no longer has a calcium deficiency.30. [-/4 Points] DETAILS MY NOTES ASK YOUR TEACHER John runs a computer software store. Yesterday he counted 121 people who walked by the store, 56 of whom came into the store. Of the 56, only 25 bought something in the store. (Round your answers to two decimal places.) (a) Estimate the probability that a person who walks by the store will enter the store. (b) Estimate the probability that a person who walks into the store will buy something. (c) Estimate the probability that a person who walks by the store will come in and buy something. (d) Estimate the probability that a person who comes into the store will buy nothing
