Cell Phone Lifetimes A recent study of the lifetimes of cell phones found the average is 24 months. The standard deviation is 4.2 months. If a company provides its 33 employees with a cell phone, find the probability that the mean lifetime of these phones will be less than 23.8 months. Assume cell phone life is a normally distributed variable, the sample is taken from a large population, and the correction factor can be ignored. Use a TI-83 Plus/TI-84 Plus calculator. Round your answer to at least four decimal places. P(X<23.8)=

A certain brand of car tends to break down on average after 115,000miles with a standard deviation of 4800 miles. If 36 cars of this brand are sampled,find the probability that their average breakdown mileage is less than 113,500miles. a. 0.0301 b. 0.3783 c. 0.6217 d. 0.9699

A bank's loan officer rates applicants for credit. The ratings are normally distributed with a mean of 200 and a standard deviation of 50.  If 64 applications are randomly selected, what is the probability that the mean credit rating of these 64 applicants will be between 205 and 275. (Round your answer to 4 decimal places.) (Calculator: http://statisticshelper.com/normal-distribution-calculator) A. 0.5011 B. 0.4113 C. 0.2119 D. 0.3664

Entrance exam scores at Cititon University are normally distributed with a mean of 552 and a standard deviation of 29. If scholarships are awarded to the top 10% of scores, what is the minimum score needed to guarantee a scholarship?

A surgery has a success rate of 90%. Suppose that the surgery is performed on threepatients Graph the probability distribution for X using a histogram.Find the mean of X.Find the variance and standard deviation of X.

The tread life of a particular brand of tire is a random variable best described by a normal distribution with a mean of 60,000 miles and a standard deviation of 2700 miles. What warranty should the company use if they want 96% of the tires to outlast the warranty?

The playing life of a Sunshine radio has a Normal distribution with a mean of 600 hours and a standard deviation of 100 hours.   What time frame would be considered unusual? What rule did you use to decide this?

In a local university, 80% of the students live in the dormitories. A random sample of 64 students is selected for a particular study. The standard deviation of p-bar is   a. 64   b. 0.05   c. 1.6   d. 0.16   e. 0.5

The Aluminum Association reports that the average American uses 56.8 pounds of aluminum in a year. A random sample of 50 households is monitored for one year to determine aluminum usage. If the population standard deviation of annual usage is 12.3 pounds, what is the probability that the sample mean will be each of the following? Appendix A Statistical Tables a. More than 60 poundsb. More than 56 poundsc. Between 55 and 57 pounds