Question

1. Anystate Auto Insurance Company took a random sample of 376 insurance claims paid out during a 1-year period. The average claim paid was $1560. Assume σ = $242.

Find a 0.90 confidence interval for the mean claim payment. (Round your answers to two decimal places.)

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Find a 0.99 confidence interval for the mean claim payment. (Round your answers to two decimal places.)

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2.Three experiments investigating the relation between need for cognitive closure and persuasion were performed. Part of the study involved administering a "need for closure scale" to a group of students enrolled in an introductory psychology course. The "need for closure scale" has scores ranging from 101 to 201. For the 78 students in the highest quartile of the distribution, the mean score was x = 178.10. Assume a population standard deviation of  σ = 7.93. These students were all classified as high on their need for closure. Assume that the 78 students represent a random sample of all students who are classified as high on their need for closure. How large a sample is needed if we wish to be 99% confident that the sample mean score is within 1.8 points of the population mean score for students who are high on the need for closure? (Round your answer up to the nearest whole number.)

3.Many people consider their smart phone to be essential! Communication, news, Internet, entertainment, photos, and just keeping current are all conveniently possible with a smart phone. However, the battery better be charged or the phone is useless. Battery life of course depends on the frequency, duration, and type of use. One study involving heavy use of the phones showed the mean of the battery life to be 12.25 hours with a standard deviation of 2.4 hours. Then the battery needs to be recharged. Assume the battery life between charges is normally distributed.

(a) Find the probability that with heavy use, the battery life exceeds 13 hours. (Round your answer to four decimal places.)


(b) You are planning your recharging schedule so that the probability your phone will die is no more than 5%. After how many hours should you plan to recharge your phone? (Round your answer to the nearest tenth of an hour.)
hours

Answer 1

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