1.  The mean of a normal probability distribustion is 500, the standard deviation is 10
    a)   About 68 % of obeservation lie between what two values
    b)   About 95 pescent of the observation lie between what two values?
    c)   Practically all of the obeservations lie between what two values?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 229, number 9)jawab distribusi normal – 13 Mei 2012 no 1
  2. The kamp family has twins, Rob and Rachel. Both Rob and Rachel graduated from college 2 years ago, and each now earning $ 50,000 per year. Rachel works in the retail industry, where the mean salary of executives with less than 5 years experience is $ 35,000 with standard deviation of $ 8,000. Rob is engineer. The mean salary of engineers with less than 5 years experience is $ 60,000 with standard deviation of % 5,000. Compute the z values for both Rob and rachel and comment on your findings
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 229, number 11) soal jawab distribusi normal – 13 Mei 2012 no 2


  3. Diketahui suatu distribusi normal baku, carilah luas di bawah kurva normal yang terletak
    a)   disebelah kiri z = 1,43
    b)   disebelah kanan z = -0.89
    c)   diantara z = -2.16 dan z =-0.65
    d)   disebelah kiri z = -1.39
    e)   disebelah kanan z = 1.96
    f)    diantara z = -0.48 dan z = 1.74
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung., halaman 177, nomor 1)soal jawab distribusi normal – 13 Mei 2012 no 3

  4. Cari nilai z bila luas dibawah kurva normal baku,
    a) 0.1131 kesebelah kiri z
    b) 0.3622 kesebelah kanan z
    c) 0.4838 antara 0 dan z, bila z > 0
    d) 0.9500 antara –z dan z, bila z > 0
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung., halaman 177, nomor 2)soal jawab distribusi normal – 13 Mei 2012 no 4

  5.  A normal distribution has a mean of 20,0 and standar devaition of 4.0
    a)   Compute the z value associated with 25.0
    b)   What proprotion of the populatiomn is between 20.0 and 25.0?
    c)   What proportion of the population is less than 18.0?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 232, number 13)soal jawab distribusi normal – 13 Mei 2012 no 5

  6.  The monthly sales of muffers in the Richmond, Virginia area the normal distribution with a mean of 1,200 and standard deviation of 225. The manufacturer would like to establish inventory level such there is only 5 percent chance of running out of stock. Where should the manufacturer set the inventory level?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 237, number 26)soal jawab distribusi normal – 13 Mei 2012 no 6

  7.  Sebuah perusahaan menggaji karyawannya rata-rata Rp 5.000,-/jam dengan variansi Rp 1500,-. Bila gaji karyawan berdistribusi normal, berapa persen
    a) Karyawan yang mempunyai gaji lebih kecil dari Rp 6.000/jam,.-
    b) Karyawan yang bergaji antara Rp 6.000 sampai dengan Rp 9.000,-
    c) Karyawan yang gajinya lebih besar dari Rp 9.000,-soal jawab distribusi normal – 13 Mei 2012 no 7
  8. Seorang sarjana peneliti dari UCLA melaporkan bahwa tikus akan berumur rata-rata 40 bulan dan variansi 6.3 bulan bila makanannya dibatasi secara ketat dan diperkaya dengan vitamin dan protein. Cari peluangnya bahwa seekor tikus yang diberikan vitamin dan protein yang cukup akan tetap hidup
    a)    Kurang dari 28 bulan
    b)    Lebih dari 32 bulan
    c)    Antara 37 dan 49 bulan
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung., halaman 178, nomor 7) soal jawab distribusi normal – 13 Mei 2012 no 8

  9. Seorang pengacara tiap hari berkendaraan ke kantornya. Rata-rata tiap arah diperlukan 24 menit dengan variansi/simpangan baku 3.8 menit (misalkan waktu perjalanan ini berdistribusi normal).
    a)    Berapa peluangnya perjalanan tersebut melebihi ½ jam
    b)    Bila kantornya buka jam 9.00 dan dia berangkat ke kantor jam 8.45 setiap hari, berapa persen dari waktu dia akan terlambat?
    c)    Bila dia berangkat jam 8.35 dan dikantor minuman kopi disajikan antara 8.30 dan 9.00, berapa peluangnya dia tidak kebagian kopi?
    d)    Cari peluang perjalanan yang diatasnya merupakan waktu 15% terlama
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung., halaman 178, nomor 11) soal jawab distribusi normal – 13 Mei 2012 no 9

  10.  Tinggi 1000 mahasiswa berdistribusi normal dengan rata-rata 174.5 cm dan simpangan baku 6.9 cm. Berapa banyak mahasiswa dapat diharapkan, yang tingginya
    a) Kurang dari 160.0 cm
    b) Antara dan termasuk 171.5 dan 182 cm
    c) Sama dengan 175.0 cm
    d) Lebih besar atau sama dengan 188 cm
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung.,halaman 179, nomor 14) soal jawab distribusi normal – 13 Mei 2012 no 10

  11.  Dalam suatu ujian metematika nilai rata-rata adalah 82 dengan simpangan baku 6.9. Semua mahasiswa yang bernilai dari 88 sampai dengan 94 mendapat nilai B. Bila nilai berdistribusi hampir normal dan delapan mahasiswa mendapat nilai B. Berapa orang yang mengikuti ujian tersebut ?
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung.,halaman 179, nomor 13)
    soal jawab distribusi normal – 13 Mei 2012 no 11

  12.  IQ 600 pelamar ke suatu perguruan tinggi berdistribusi normal dengan rata-rata 115 dan simpangan baku 12. Berapa pelamar yang akan ditolak, jika perguruan tinggi tersebut hanya menerima IQ lebih besar dari 110 ?
    (Ronald E Walpole, Raymond h Myers., Ilmu Peluang dan Staistika untuk Insinyur dan Ilmuwan., Edisi Keempat, Penerbit ITB bandung.,halaman 180, nomor 19)soal jawab distribusi normal – 13 Mei 2012 no 12

  13. The accounting department of Weston materilas, Inc., a national manufacturer of unattached garages, reprts that its takes two construction workers a mean of 32 hours and standard deviation of 2 hours to erect the red Barn model. Assume the assembly times follow the normal distribution
    a.    Determine the z value for 29 and 34 hours. What percent of the garage take between 32 hours and 34 hours to erect?
    b.    What percent of garages take between 29 hours and 34 hours to erect?
    c.    What percent of the garages take 28.7 hours or less to erect?
    d.    Of the garages, 5 percent take how many hours or more to erect
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 42) soal jawab distribusi normal – 14 april 2013 no 13
  14. A study of long distance phone calls made from the corporate offices of Pepsi Bottling Group, Inc, in Somers, New York, revealed the length of the calls in minutes, follows the normal probability distribution. The mean lenght of time per call was 4.1 minutes and the standard deviation was 0.60 minutes.a.    What fraction of the calls last between 4.2 and 5 minutes?
    b.    What fraction of the calls last more than 5 minutes?
    c.    What fraction of the calls last between 5 and 6 minutes?
    d.    What fraction of the calls last between 4 and 6minutes?
    e.    As part of the reports to the president, the director of communications would like to repor the length of the longest (in duration) 4 percent og the calls. What is this time ?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 44) soal jawab distribusi normal – 14 april 2013 no 14
  15. The annual commisions earned by sales representatives of Machine product. Inc., a manufacturer of light machinery, follow the normal probability distribution. The mean yearly amount earned is $ 40,000 and the standar deviation is $ 5,000
    a.    What percent of the sales representatives earn more than $ 42,000 per year?
    b.    What percent of the sales representatives earn between $ 32,000 and $ 42,000 per year?
    c.    What percent of the sales representatives earn between $ 32,000 and  $ 35,000 per year?
    d.    Tha sales manager ward to award the sales representatives who earn the largest commsions a bonus of $ 1,000. He can award a bonus to 20 percent of the representatives. What is the cutoff point betweem those who earn a bonus and those who dont ?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 46) soal jawab distribusi normal- 14 april 2013 no 15
  16. According to a goverment study among adults in the 25 to 34 years age group, the mean amount spend per year on reading and entertainment is $ 1,994. Assume that the distribution of the amounts spent follows the normal distribution with a standar deviation of $ 450.
    a.    What percent of the adults spend more than $ 2500 per year on reading and entertainment?
    b.    What percent spend between $ 2,500 and $ 3,000 per year on reading and entertainment?
    c.    What percent spend less than $ 1,000 per year on reading and entertainment?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 245, number 48) soal jawab distribusi normal – 14april 2013 no 16
  17. Fast Service Truck Lines uses the Ford Super Duty F-750 exclusively. Management made a study of the maintenance costs and determined the number miles travel during the year followed the noemal distribution. The mean of the distribution was 60,000 miles and the standard deviation 2,000 miles?
    a.
    What percent of the Ford Super Duty F-750s logged 65,200 miles or more?
    b.    What percent of the trucks logged more than 57,060 but less than 58,280 miles?
    c.    What percent of the Fords traveled 62,000 miles or less during the year?
    d.    Is is reasonable to conclude that any of the trucks were driven more than 70,000 miles. Explain
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 54) soal jawab distribusi noemal – 14 april 2013 no 17
  18.  A recent report in BusinessWeek indicated that 20 percent of all employees steal frpm their company each year. If a company employs 50 people, what is the probability that
    a.    Fewer than 5 employees steal
    b.    More than 5 employees steal
    c.    Exactly 5 employees steal
    d.    More than 5 but fewer than 15 employees steal
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 52) soal jawab distribusi normal – 14 april 2013 no 18 
  19. It is  estimated that 10 percent of those taking the quantitative methods portion of the CPA examination fail that section. Sixty student are taking the exam this Saturday.
    a.    How many would you expect to fail ? what is the standar deviantion ?
    b.    What is the probability that exectl;y two students will fail?
    c.    What is the probability at least two students will fail ?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 54) soal jawab distribusi normal – 14 april 2013 no 19 
  20. Cruise ships of the Royal Viking line report that 80 percent of their rooms are occupied during September. For a cruise ship having 800 rooms, what is the probability that 665 or more are occupied in September ?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 56)soal jawab distribusi normal – 14 april 2013 no 20 
  21. The funds dispended at the ATM machine located near the chekout line at the Kroger’s in Union Kentucky, follows a normal distribution with a mean of $4,200 per day and a standard deviation of $ 720 per day. The machine is programmed to notify the nearby bank if the amount dispended is very low (less than $ 2,500) or very high (more than $ 6,000)
    a.    What percent of the days will the bank be notified because the amount dispended is very low?
    b.    What percent of the days will the bank be notified because the amount dispended is very high?
    c.    What percent of the days will the bank not be notified regarding the amount of funds dispersed ?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 58) soal jawab distribusi normal – 14 april 2013 no 21 
  22. The Cincinnati Enquirer , in its Sunday business supplement, reported that the mean number of hour worked per week by those employed full time is 43.9. The article further indicated that about one-third of those employed full time work less than 40 hours per week.
    a.    Given this information and assuming that number of hours worked follows the normal distribution, what is the standard deviation of the number of fours worked?
    b.    The article also indicated that 20 percent of those working full time work more than 49 hours petr week. Determine the standard deviation with this information. Are the two estimates of the standard deviation are similiar? What would you conclude
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 244, number 60)) soal jawab distribusi normal – 14 april 2013 no 22

  23. The price of shares of Bank of Florida at the end of trading each day for the last year followed the normal distribution. Assume there were 240 trading days in the year. The mean price was $ 42.00 per share and the standard deviation was $ 2.25 per share
    a.    What percent of the days was the price over $ 45.00 ? How many days would you estimate
    b.    What percent of the days was the price between $ 38.00 and $ 40.00
    c.    What was the stock’s price on the highest 15 percent of the days?
    (Lind, Marchal, Wathen., Statistical Techniques in Business and Economics., Mc Graw Hill, fourteent Edition., Page 246, number 62)) soal jawab distribusi normal – 14 april 2013 no 23
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