1. Math - Standard Deviation

    A General Electric soft white 3-way bulb has an average life of 1200 hours with a standard deviation of 50 hours. Find the probability that the life of one of these bulbs will be between 1150 and 1300 hours. You need to change the times to Z-scores
  2. Statistics

    An industrial engineer has found that the standard household light bulbs produced by a certain manufacturer have a useful life that is normally distributed with a mean of 250 hours and a variance of 2500. (a) What is the probability that a randomly
  3. math

    1) A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours. A sample of 100 light bulbs from the company were tested and the researcher found that the average life of each light bulb
  4. Management

    The bulbs manufactured by a company gave a mean life of 3000 hours with standard deviation of 400 hours. If a bulb is selected at random, what is the probability it will have a mean life less than 2000 hours? Question: 1) Calculate the probability. 2) In
  5. maths

    the life span of an electric bulb is normally distribution with mean 5500 light hours and standard deviation of 1200 light hours . what is the probability that a randomly selected bulb which lasts more than 6000 light hours?
  6. Statistics

    The life of an electric light bulb is known to be normally distributed with a mean of 2000 hours and a std. of 120 hours. Find the probability that the life of such a bulb would be. (a) greater than 2150 hours (b) within the range of 1850 hours to 2090
  7. statistics

    A new extended-life light bulb has an average service life of 750 hours, with a standard deviation of 50 hours. If the service life of these light bulbs approximates a normal distribution, about what percent of the distribution will be between 600 hours
  8. statistics, help

    Can someone help me which way can I approach this problem. A hint of a formula or anything would be helpful... Life of Light Bulbs A certain type of light bulb has an average life of 500 hours, with a standard deviation of 100 hours. The length of life of
  9. statisitics

    A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. How many bulbs should have a life expectancy between 400 and 600 hours?
  10. probability and statistics

    An electrical firm manufactures light bulbs that have a usuable life that is normally distributed with a mean of 1000 hours and a standard deviation of 80 hours. Find the probability that a package of 4 bulbs would last at least 4400 hours.
  11. Statistics

    An electrical firm which manufactures a certain type of bulb wants to estimate its mean life. Assuming that the life of the light bulb is normally distributed and that the standard deviation is known to be 40 hours, how many bulbs should be tested so that
  12. statitics

    a light bulb manufacture gaurentees that the mean life of a certain type of bulb is at least 875 hours. A random sample of 40 light bulbs has a mean life of 863 hours with a standard deviation of 50. a=0.04
  13. statistics

    the life of light bulbs is distributed normally. The variance of the life time is 225 and the mean lifetime of a bulb is 590 hours. Find the probability of a bulb lasting for at most 603 hours. Yeah, WTF??? Why me!??!
  14. stat

    A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time. 77) At least 500
  15. Stats

    A new extended-life light bulb has an average service life of 750 hours, with a standard deviation of 50 hours. If the service life of these light bulbs approximates a normal distribution, about what percent of the distribution will be between 600 and 900
  16. Statistics

    Construct a 99% confidence interval for life expectancy of a new GE light bulb. 64 bulbs are randomly selected and a mean of 750 hours and a standard deviation of 20 hours is found. Assume the distribution of life expectancy is normally distributed.
  17. Math ---HELP!!!!!

    light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, use the 68-95-99.7 rule to approximate the percentage of light bulbs having a life between 2000 hours and 3500 hours? A. About 13.5% B.
  18. Math

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, use the 68-95-99.7 rule to approximate the percentage of light bulbs having a life between 2000 hours and 3500 hours? A. About 13.5% B.
  19. Math

    A company makes batteries with an average life span of 300 hours with a standard deviation of 75 hours. Assuming the distribution is approximated by a normal curve fine the probability that the battery will last . Less than 250 hours b. Between 225 and 375
  20. Statistics

    A company makes batteries with an average life span of 300 hours with a standard deviation of 75 hours. Assuming the distribution is approximated by a normal curve fine the probability that the battery will last . Less than 250 hours b. Between 225 and 375
  21. Math

    A consumer buys n light bulbs, each of which has a lifetime that has a mean of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming independence of the lifetimes,
  22. Math

    A consumer buys n light bulbs, each of which has a lifetime that has a mean of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming independence of the lifetimes,
  23. Math ---HELP!!!!!

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours? A. About 84% B. About 68% C. About 32% D. About 16%
  24. Math

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours? A. About 84% B. About 68% C. About 32% D. About 16%
  25. sTATISTICS

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours?
  26. Math

    A company makes batteries with an average life span of 300 hours with a standard deviation of 75 hours. Assuming the distribution is approximated by a normal curve fine the probability that the battery will last:(give 4 decimal places for each answer) a.
  27. statistics

    7) Your employer, Woodbridge Electric Inc., wants to offer a warranty on the new compact fluorescent light bulb that they have produced and tested. You are called into a meeting and operational experts provide the following data: mean bulb life = 8000
  28. Probablity

    The life time of a certain kind of batteries has a mean life of 400 hours and standard deviation as 45 hours. Assuming the distribution of life to be normal, find i) the percentage of batteries with a life time of atleast 470 hours. Ii) Out of 10000
  29. Business Statistics

    The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The manufacturer's specifications are that the standard deviations is 100 hours. A random sample of 64 light bulbs indicated a sample
  30. Math

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours? A. About 25% B. About 50% C. About 75% D. About 68% Answer B
  31. Math ---HELP!!!!!

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours? A. About 25% B. About 50% C. About 75% D. About 68% Answer B
  32. statistics

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours?
  33. math

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours?
  34. Statistics

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours
  35. stats

    If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours? A) About 25% B) About 50% C) About 75% D) About 68%
  36. statistics

    Solve the problem. The lifetime of a new brand of light bulb can be described by a Normal model with a mean of 2000 hours and a standard deviation of 250 hours. Find the percentage of light bulbs that will last more than 2600 hours. A.) 100% B.) 5% C.)
  37. statistics

    The numbers of hours of life of a torch battery is normally distributed with a mean of 150 hours and standard deviation of 12 hours. In a quality control test, two batteries are chosen at random from a batch. If both batteries have a life less than 120
  38. Statistics

    The mean life expectancy of a certain type of light bulb is 945 hours with a standard deviation of 21 hours. What is the approximate standard deviation of the sampling distribution of the mean for all samples with n=50?
  39. Probability and Statistics

    For questions 1- 5 use confidence intervals to test the hypothesis. 1) A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours. A sample of 100 light bulbs from the company were tested
  40. calculus

    A MANUFACTURE OF LIGHTBULBS HASS SAMPLED 40 BULBS IN ORDER TO DETERMINE THE POPULATION MEAN LIFE OF THE BULBS. tHE SAMPLE MEAN WAS 1200 HOURS WITH A STANDARD DEVIATION OF 100. tHE MANUFACTURER WOULD LIKE TO KNOW, WITH 95% CONFIDENCE, THE INTERVAL VALUES
  41. statistics

    The lifetime of a type of electric bulb has expected value µ = 475 hours and standard deviation σ = 60 hours. (a) Use the central limit theorem to determine the expected value and standard deviation of the sample mean of n such lightbulbs where n = 100,
  42. statistics

    The duration of time it takes General Motors to build a car is normally distributed with a mean of 31 hours and a standard deviation of 2 hours. a) What is the probability that a single car, selected at random, will take between 28 and 34 hours? b) What is
  43. Probability Statistics

    a manufacturing plant uses 3000 light bulbs whose lifetimes are independently normally distributed with mean 500 hrs, and standard deviation 50 hrs. to minimize the number of bulbs that burn out during production hours, all bulbs are replaced after given
  44. Statistics

    A certain type of lightbulb is advertised to have an average lifetime of 1,000 hours. Assume the lifetimes of these lightbulbs are approximately normally distributed with a standard deviation of 250 hours. A) Find the percentage of lightbulbs that will
  45. Probability & Statistics

    The life expectancy (in hours) of a fluorescent tube is normally distributed with a mean 8000 and a standard deviation 1000. Find the probability that a tube lasts for more than 11000 hours.
  46. economics 7

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice compared to competitor
  47. economics

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice compared to competitor
  48. economics (7)

    An electronics company advertises that the battery life of its new smart phone with normal usage averages 72 hours. The company says this is one of the desirable characteristics of the phone which makes the phone a better choice compared to competitor
  49. statistics

    2. The new Twinkle bulb has a standard deviation hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be 492 hours. a. Find the margin of error E for a 90% confidence interval. Round your answer to the nearest
  50. statistics

    Suppose that the certain lifetimes of a certain light bulb are normally distributed with μ=1500 hours and σ=200. Find the probability that a light bulb will burn out in less than 1200 hours.
  51. statistics

    The lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has lifetimes that lie within 1 standard deviation of the mean on either side?
  52. math

    2) The lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has lifetimes that lie within 1 standard deviation of the mean on either side?
  53. statistics

    researchers believe a new sleep on average 10 hours per night ( µ = 10), with a population standard deviation of 2.3 hours(s=2.3) it is assume that the number of hours of sleep per night is normal distributed , however you think this drug causes people to
  54. economics

    i have some questions please help Transportation equipment that was purchased in 2004 for $200,000 must be replaced at the end of 2009. what is the estimated cost of the replacement, based on, the following equipment cost index: Year INDEX YEAR INDEX 2004
  55. Statistics

    The lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side? Apply
  56. Statistics

    The lifetimes of projector bulbs of a particular type are normally distributed with a mean of 470 hours and a standard deviation of 15 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side?
  57. Ashworth college

    The lifetimes of light bulbs of a particular type are normally distributed with a mean of 270 hours and a standard deviation of 11 hours. What percentage of the bulbs has lifetimes that lie within 2 standard deviations of the mean on either side? Apply the
  58. statistics

    A manufacturer of light bulbs has sampled 40 bulbs in order to determine the population mean life of the bulbs. The sample mean was 1,200 hours with a standard deviation of 100. The manufacturer would like to know, with 95% confidence, the interval values
  59. statistics

    6. According to the records of Enersource, an electric company serving the Mississauga area, the mean electricity consumption for all households during winter is 1650 kilowatt-hours per month. Assume that the monthly electricity consumption during winter
  60. Statistics

    A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 692 hours with a sample standard deviation of 30 hours. It is reasonable to believe that the
  61. statistics

    1. The new Twinkle bulb has a standard deviation σ = 34 hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be x= 492 hours. Question: Find the margin of error E for a 90% confidence interval. Round your
  62. statistics

    A 4 to 7 month old baby sleeps an average of 14 hours per day. At this age, babies sleep patterns follow normal distribution with the standard deviation of 1.6 a) is it unusual for a baby to sleep under 12 hours aday? b) In a random sample of 10 babies of
  63. Statistics

    the average numbers of hours a cat sleep is approximately normally distributed with a mean of 15 hours and a standard deviation of 1.7 hours; what percentage of cats sleep between 13 and 18 hours
  64. Statistics

    Can anyone tell me how to use TI-84 calculator to solve this problem??? A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 692 hours with a sample
  65. Stats

    I am working on a review sheet and got everything except for this one. I am not sure whether to use z or t. The number of hours per week that high school juniors watch TV is normally distributed with a mean of 8 hours and a standard deviation of 2 hours.
  66. Statistics

    A survey was conducted to determine the number of hours people listen to the radio. While most of the listening is in the car, it turns out that the mean is 2.5 hours with a standard deviation of 0.75 hours. Find the probability that the sum of 80 values
  67. Stats

    A survey was conducted to determine the number of hours people listen to the radio. While most of the listening is in the car, it turns out that the mean is 2.5 hours with a standard deviation of 0.75 hours. Find the probability that the sum of 100 values
  68. statistics

    Urgen!! Statistics homework help? Your company is producing special battery packs for the most popular toy during the holiday season. The life span of the battery pack is known to be Normally distributed with a mean of 250 hours and a standard deviation of
  69. Statistics (37)

    According to the Sleep Foundation, the average night's sleep is 6.8 hours (Fortune, March 20, 2006). Assume the standard deviation is .7 hours and that the probability distribution is normal. a. What is the probability that a randomly selected person
  70. Economics (37)

    According to the Sleep Foundation, the average night's sleep is 6.8 hours (Fortune, March 20, 2006). Assume the standard deviation is .7 hours and that the probability distribution is normal. a. What is the probability that a randomly selected person
  71. Statistics

    The lifetime of a certain smart phone battery has an unknown distribution with mean value of 8 hours and standard deviation of 2 hours. What is the approximate probability that the average battery lifetime of a sample of 36 batteries will exceed 8.1 hours?
  72. Statistics

    The lifetime of a certain smart phone battery has an unknown distribution with mean value of 8 hours and standard deviation of 2 hours. What is the approximate probability that the average battery lifetime of a sample of 36 batteries will exceed 8.1 hours?
  73. adult education

    The lifetimes of lightbulbs of a particular type are normally distributed with a mean of 290 hours and a standard deviation of 6 hours. What percentage of the bulbs have lifetimes that lie within 1 standard deviation to either side of the mean?
  74. Statistics

    The lifetimes of batteries produced by a firm are known to be normally distributed with a mean of 100 hours and a standard deviation of 10 hours. What is the probability a battery will last between 110 and 120 hours?
  75. Statistics

    For the manufacturing plant discussed in Exercise 8.10, the union president and the human resources director jointly select a simple random sample of 36 employees to engage in a discussion with regard to the company’s work rules and overtime policies.
  76. Statistics

    8.11) For the manufacturing plant discussed in Exercise 8.10, the union president and the human resources director jointly select a simple random sample of 36 employees to engage in a discussion with regard to the company’s work rules and overtime
  77. Statistics

    For the manufacturing plant discussed in Exercise 8.10, the union president and the human resources director jointly select a simple random sample of 36 employees to engage in a discussion with regard to the company’s work rules and overtime policies.
  78. statistics

    A 4 to 7 month old baby sleeps an average of 14 hours per day. At this age, babies sleep patterns follow normal distribution with the standard deviation of 1.6 a) is it unusual for a baby to sleep under 12 hours a day? b) In a random sample of 10 babies of
  79. math

    A recent survey shows that the average man will spend 141,288 hours sleeping, 85,725 hours working, 81,681 hours watching television 9,945 hours commuting, 1,662 hours kissing, and 363,447 hours on other tasks during his lfetime. What percent of his life,
  80. STATISTICS HELP

    The lifetime of a disk drive head is normally distributed with a population mean of 1000 hours and standard deviation of 120 hours. Determine the probability that the average lifetime for 9 disk drives will exceed 940 hours. Need to see work!
  81. statistics

    In a random sample of 50 babies 4 to 7 month old the average number of hours they slept per day turned out to be 14.2 hours with a standard deviation of 1.6 hours find and interpret a 90% confidence interval for the mean number of hours slept by babies at
  82. statistics

    In a random sample of 50 babies 4 to 7 month old the average number of hours they slept per day turned out to be 14.2 hours with a standard deviation of 1.6 hours find and interpret a 90% confidence interval for the mean number of hours slept by babies at
  83. Math

    Home Depot sells compact fluorescent lamps (CFLs) that have a mean life of 10,000 hours with a standard deviation of 1,000 hours. In an order of 8,000 lamps, how many can be expected to last 11,000 hours or longer?
  84. statistics

    A survey was conducted to measure the number of hours per week adults spend on home computers. In the survey, the number of hours was normally distributed, with a mean of 8 hours and a standard deviation of 1 hour. A survey participant is randomly
  85. statistics

    3. The personnel director of a corporation will study the overtime work during the previous year for the 2,575 clerical workers. A sample of 100 of these workers will be chosen at random from the files. The average and the standard deviation of the
  86. statistics

    The life span of the battery pack is known to be Normally distributed with a mean of 250 hours and a standard deviation of 20 hours. How to find the percentage of the battery packs lasting more than 250 hrs.
  87. Statistics

    A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Cavalier shows that the mean is 4.5 hours and the standard deviation is .6 hours. If 42 mechanics are randomly selected, find the probability that their mean rebuild
  88. Statistics

    The amount of time the university professors devote to their jobs per week is normally dis- tributed with a mean of 52 hours and a standard deviation of 8 hours. (a) What is the probability that a professor works for more than 56 hours per week? (b) Find
  89. Qvntitative Methods

    CASE STUDY: 1 The bulbs manufactured by a company gave a mean life of 3000 hours with standard deviation of 400 hours. If a bulb is selected at random, what is the probability it will have a mean life less than 2000 hours? Question: 1) Calculate the
  90. Statistics

    An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life for a particular use before they failed is 19.0 hours. The distribution of the lives approximated a normal distribution. The standard deviation of the
  91. stats

    a study of the amount of time it takes a mechanic to rebuild the transmission of a 1992 chevrolet cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours. if 40 mechanics are randomly selected, find the probability that their mean
  92. statistics

    The average time to sew a pair of pants is 4.2 hours with a standard deviation of 30 minutes and if the distribution is normal then the probability of a worker finishing the pants in less than 3 hours is.
  93. statistics

    A company that manufacturers bookcases finds that the average time it takes an employee to build a bookcase is 23 hours with a standard deviation of 8 hours. A random sample of 64 employees is taken. What is the likelihood that the sample mean will be 18
  94. Statistics

    Exponential distribution was used to model the lengths of CD-ROM drives in a two drive system. The two CD-ROM drives operate independently, and at least one drive must be operating for the sytem to eperate successfully. Both drives have a mean length of
  95. math,

    Exponential distribution was used to model the lengths of CD-ROM drives in a two drive system. The two CD-ROM drives operate independently, and at least one drive must be operating for the sytem to eperate successfully. Both drives have a mean length of
  96. Stats

    Exercise 6-8 The Downtown Parking Authority of Tampa, Florida, reported the following information for a sample of 235 customers on the number of hours cars are parked and the amount they are charged. Number of Hours Frequency Amount Charged 1 18 $3 2 33 7
  97. Math

    A certain type of thermal battery for an airplane navigation device backup power has a mean life of 300 hours with a standard deviation of 15 hours. Assume a normal distribution of backup power device lives. What proportion of these batteries can be
  98. Math

    A certain type of thermal battery for an airplane navigation device backup power has a mean life of 300 hours with a standard deviation of 15 hours. Assume a normal distribution of backup power device lives. What proportion of these batteries can be
  99. linear/exponential

    This question involves the half-life formula. In this exercise, we are to give a half-life for an exponentially decaying quantity. Need answer to the following: The half-life of a drug in the bloodstream is 4 hours. By what factor does the concentration of
  100. statistics

    The accounting department at Weston Materials, Inc., a national manufacturer of unattached garages, reports that is takes two construction workers a mean of 32 hours and a standard deviation of 2 hours to erect the red barn model. Assume the assembly times