Author:
Christine Farr

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Data File 3Show all workChapter Five1) If light bulbs have lives that are normally distributed with a mean of 2500 hours and astandard deviation of 500 hours, what percentage of light bulbs have a life less than 2500hours?2) The lifetimes of light bulbs of a particular type are normally distributed with a mean of370 hours and a standard deviation of 5 hours. What percentage of bulbs have lifetimesthat lie within 1 standard deviation of the mean on either side?3) The amount of Jen’s monthly phone bill is normally distributed with a mean of $60 and astandard deviation of $12. Fill in the blanks:68% of her phone bills are between $______________ and $______________.4) The amount of Jen’s monthly phone bill is normally distributed with a mean of $50 and astandard deviation of $10. Find the 25th percentile.5) The diameters of bolts produced by a certain machine are normally distributed with amean of 0.30 inches and a standard deviation of 0.01 inches. What percentage of boltswill have a diameter greater than 0.32 inches?6) The annual precipitation amounts in a certain mountain range are normally distributedwith a mean of 88 inches, and a standard deviation of 10 inches. What is the likelihoodthat the mean annual precipitation during 25 randomly picked years will be less than 90.8inches?7) A final exam in Statistics has a mean of 73 with a standard deviation of 7.73. Assumethat a random sample of 24 students is selected and the mean test score of the sample iscomputed. What percentage of sample means are less than 70?8) A mean score on a standardized test is 50 with a standard deviation of 10. Answer thefollowinga. What scores fall between –1 and +1 standard deviation?b. What percent of all scores fall between –1 and +1 standard deviation?c. What score falls at +2 standard deviations?d. What percentage of scores fall between +1 and +2 standard deviations?Show all workChapter Six1) For the following questions, would the following be considered “significant” if itsprobability is less than or equal to 0.05?a. Is it “significant” to get a 12 when a pair of dice is rolled?b. Assume that a study of 500 randomly selected school bus routes showed that 480arrived on time. Is it “significant” for a school bus to arrive late?2) If you flip a coin three times, the possible outcomes are HHH, HHT, HTH, HTT, THH,THT, TTH, and TTT. What is the probability of getting at least one head?3) A sample space consists of 64 separate events that are equally likely. What is theprobability of each?4) A bag contains 4 red marbles, 3 blue marbles, and 7 green marbles. If a marble israndomly selected from the bag, what is the probability that it will be blue?5) The data set represents the income levels of the members of a country club. Estimate theprobability that a randomly selected member earns at least $98,000.112,000112,00086,000119,000126,00098,000105,00098,00090,00082,000140,000154,000133,000147,00094,00078,00094,000182,000126,000119,000

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