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Statistik Industri [6] October 18, 2008

Posted by desrinda in Statistik Industri.
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ESTIMATION PROBLEMS

A point estimate is a single number. For the population mean (and population standard
deviation), a point estimate is the sample mean (and sample standard deviation).

A confidence interval provides additional information about variability.

PR:

1. What is meant by “the sampling distribution of the mean”?
2. What does the central limit theorem say? Why is it useful?
3. How is the population mean of the sample average related to the population mean of individual observations?
4. What is the standard error of the mean, and what do we use it for?
5. What happens to the sampling distribution of the mean if (i) the sample size is increased, (ii) the population standard deviation is decreased?
6. Using  4 your Standard Normal table, verify that :
– 90 % of the area under the standard normal curve (i.e N(0,1) corresponds to Z= ± 1.65;
– 95 % of the area under the standard normal curve corresponds to Z = ± 1.96
– 99 % of the area under the standard normal curve corresponds to Z = ± 2.58
7. Students in MA238 spend on average 3.75 hours a week studying ( with a population standard deviation σ = 5.17 )
i. Given this fact, describe the sampling distribution of the mean if all possible random sample size 50 were chosen.
ii. What can you say about the mean off all the possible sample means?
iii. If 250 such samples were chosen at random and for each you calculated a 95% C.I for the mean, how many such intervals would you expect to contain the true mean?
iv. If instead you calculated a 99% C.I. for the mean, how many intervals would you now expect to capture the true mean.
v. Would you expect the 99% C.I. for the mean to be narrower or wider than the corresponding 95 % C.I. for the mean. Justify your answer!
8. The director of quality at a light bulbs factory needs to estimate the average life of a large shipment of light bulbs. A random sample of 64 light bulbs indicated a sample average life 350 hours with sample standard deviation of 100 hours.
a) Construct and interpret a 95% confidence interval estimate of the true average life of light bulbs in this shipment.
b) Do you think the manufacturer has the right to state that the light bulbs last an average 400 hours? Explain.
c) Does the population have to be normally distributed here for the interval to be valid? Explain.
d) Explain why an observed of 320 hours is not unusual, even thought it outside it is outside the 95% confidence interval you have calculated.
e) Suppose that the sample average had been 300 hours. What would be your answer to a) ?
9. A newspaper headline describing a poll of registered voters taken two weeks before a recent election reads “Aitchison lead with 525. The accompanying article describing the poll state that the margin of the error was 2% with 95% confidence.
a) Explain in plain language to someone who knows no statistics what “95% confidence “ means?
b) The poll shows Aitchison leading. But the newspaper article said that the election was too close to call, Explain why?
10. A student  reads that a 95% confidence interval for the mean maths score leaving sert students in 45 to 47 %. Asked to explain the meaning of this interval, the student says, 95% of leaving cert students have math score between 451 and 47%. Is the student right? Justify your answer.

Organisasi Industri [6] October 18, 2008

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Kuliah ke-6 dalam semester ini, Pak Yuri membahas Bab 16-nya Robbins.

Teori-teori motivasi yang kami diskusikan:

1. Maslow’s Hierarchy of Needs

2. McGregor’s Theory X and Theory Y

Theory X
Assumes that workers have little ambition, dislike work, avoid responsibility, and require close supervision.
Theory Y
Assumes that workers can exercise self-direction, desire responsibility, and like to work.

 

3. Herzberg’s Motivation-Hygiene Theory

Job satisfaction and job dissatisfaction are created by different factors.
Hygiene factors: extrinsic (environmental) factors that create job dissatisfaction.
Motivators: intrinsic (psychological) factors that create job satisfaction.

Contemporary Theories:
– Three-Needs Theory
– Goal-Setting Theory
– Reinforcement Theory
– Designing Motivating Jobs
– Equity Theory
– Expectancy Theory

Terms on “job” have been learned so far:
Job specification => related to qualification
Job analysis => how one’s doing the job
Job description => detailing one’s responsibility + authority
Job design => a way to motivate employee

Teknik Kuantitatif [6] October 17, 2008

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Dalam kuliah Jumat malam (17 Oktober 2008) yang lalu, kami dibagikan hardcopy materi baru: Programa Integer dan Programa Dinamis. Tapi Pak Amar masih melanjutkan pengajarannya mengenai Model Transportasi.

Contoh soal:

X akan mengirim barang dari 3 sumber pengiriman menuju ke 3 tujuan. Jumlah barang dari ketiga sumber dan jumlah permintaan dari tujuan adalah seperti pada tabel.

Pada tabel di bawah ini diberikan keuntungan per unit yang diperoleh jika barang dikirim dari setiap sumber menuju tujuan. Selesaikanlah dengan metode transportasi.

BTW kayaknya makin jauh aja nih saya dari yang namanya “pemahaman”. Untungnya (?) kuis yang seharusnya Sabtu sore (18 Oktober 2008) akhirnya diundurkan ke minggu berikutnya. However, rasanya kok bakalan sama saja…hanya akan menjadi “kegagalan yang tertunda” hahahaha…(orang kata khan kegagalan adalah “sukses yang tertunda”?).

Haddduuuhh…gw salah jurusan kali ya? Istilahnya temen-temen (Pak Sigit dan Pak Dhedhi), nggak cocok nih secara weton :))

Manajemen Operasi [6] October 17, 2008

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Pak Yadrifil menghabiskan bahan pelajaran mengenai Critical Path Analysis (Ch.3 buku Chase, exhibit 3.9-3.11). Setelah itu, sesuai dengan janjinya, beliau membagikan soal-soal kuis.

BAGIAN I (5 soal mengenai teori, berbobot masing-masing 8 point)

1.
Sebutkan 4 s/d 7 jenis transformasi pada sistem produksi dalam bentuk tabel SIRTO (System, Input, Resources, Transformation, Output) disertai contohnya masing-masing.
Jawab:
Ini mah kudu inget jenis-jenis transformasi yang dibagi-bagi menjadi PLESPPI = physical, location, exchange, storage, physiological, psychological, information.

2.
a) Sebutkan 3 s/d 4 pilar proyek yang merupakan project objectives/targets perusahaan.
b) Sebutkan juga 7 s/d 12 project aspects yang berisiko bagi pencapaian project objectives/targets tsb.
Jawab:
a) Time, cost, performance, EHS
b) Banyak nih, misalnya kekurangan supply material.

3.
Identifikasikan tahap-tahap yang merupakan proses value added maupun non-value added yang merupakan pemborosan (waste) yang biasa terjadi pada suatu kegiatan batch production.
Jawab:
I wish that I had read this earlier from our reference, sayang sekali nggak bisa menjabarkan dengan benar proses yang terdiri queue, inspection, setup, run dst.

4.
Definisikan kapan dimulai dan diakhirinya 8 s/d 10 proses (business process) berikut, sehingga berdasarkan identifikasi tersebut kita akan bisa menganalisa dan meningkatkan added value atau performance business proses tersebut.
Jawab:
- Customer service = customer arrival until departure
– Product development = research until launch
– Manufacturing = production planning until delivery
– etc.

5.
Sebutkan 5 dimensi dari kebutuhan customer (sesuai dengan buku Chase).
Jawab:
– Flexibility
– Cost (price)
– Quality
– Delivery
trus apa ya satu lagi tadi?

BAGIAN II (3 soal perhitungan, berbobot masing-masing 20 point)

1. Mengenai multistage process, harus menghitung output per hari dari keseluruhan proses, efisiensi proses berdasarkan output rate, throughput time, dan output per hari dari salah satu prosesnya.

2. Mengenai antrian pada proses teller dalam case study Bank BNI, yang ditanyakan adalah:
– Berapa output maksimum pada periode tersebut?
– Dapatkah bank memproses seluruh nasabah pada akhir periode?
– Berapa waktu tunggu maksimum untuk nasabah?
– Pada periode waktu mana waktu tunggu maksimum terjadi?

3. Wah, soal terakhir ini mah gile bener…sebenarnya sederhana, hanya menggambarkan AON (activity on node) kegiatan sehari-hari sepasang suami istri. Berhubung sekelas tidak ada yang menyelesaikannya, maka dijadikan PR untuk dikumpulkan pada minggu berikutnya.

Activity List Getting The Brady’s To Work   
Performed by Mr. Brady:
1. Alarm goes off
2. Get up, shut off alarm, turn up heat
3. Return to bed until wife finishes showering
4. Get up, shower, and shave
5. Get dressed
6. Prepare breakfast
7. Eat breakfast
8. Brush teeth
9. Put on tie and coat
10. Pick up briefcase, hat, and lunch
11. Warm up the car and get it out of garage
12. Leave for work with wife

Performed by Mrs. Brady:  
13. Get up, shower
14. Blow-dry and comb hair
15. Apply makeup
16. Get dressed
17. Straighten up bedroom
18. Feed the parrot
19. Eat breakfast
20. Prepare and pack the lunches
21. Brush teeth
22. Put on lipstick
23. Turn down heat, and pick up lunch
24. Lock front door
25. Get into car to go to work

Kenapa saya jawabannya bisa ngaco sih? Udah keburu mumet kali ya?

Statistik Industri [5] October 12, 2008

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Sesuai janjinya, Ibu Arian Dhini memberikan quiz. Soalnya diambil dari topik distribusi Poisson dan distribusi normal.

Manajemen Operasi [5] October 12, 2008

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Project Analysis & Network  Diagram => Chapter 3 dari bukunya Chase. Must not forget, there will be a quiz on this class…next week (October 17, 2008).

Teknik Kuantitatif [5] October 12, 2008

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Model Transportasi (modul ke-4 dari bahan kuliah Pak Amar) dibahas dalam kuliah hari itu. Untungnya beliau mengerti kesulitan (?) kami memahami pelajaran dalam penyelesaian programa linear ini, sehingga mulai minggu berikutnya akan diusahakan ada responsi dengan asisten dosennya.

Sebenarnya sih, mestinya kita juga rajin belajar dan latihan soal juga sendiri-sendiri ya?

Berpikir Sistem [3] October 12, 2008

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I’ve missed the class. Kata temen-temen sih, topiknya mengenai “berpikir kreatif”.

Pertama kalinya dalam semester ini, saya nggak ikutan kuliah. Alasannya? It’s stupid, actually…karena bikin tugas yang harus dikumpulkan sekaligus untuk 3 mata kuliah pada hari itu (Manajemen Operasi, Statistik Industri, Ekonomi Teknik). Tugas-tugas tersebut adalah PR sebagai pengganti kuliah yang ditiadakan karena libur lebaran minggu sebelumnya (3-4 Oktober 2008).

BTW kok “berpikir” aja ternyata mesti dipikirin ya? Hehehehe…

Organisasi Industri [5] October 12, 2008

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Pak Yuri masih menyelesaikan pembahasan Bab 15 dari file MS Power Points-nya Robbins. Masuk ke bahasan work group behaviour, dijelaskan kondisi-kondisi eksternal maupun internal variables yang mempengaruhinya.

Mengenai group structure, yang mesti dipahami adalah setiap group memiliki role (peranan yang diharapkan dijalankan oleh masing-masing anggotanya), norms (meliputi standar dan ekspektasi terhadap kinerja, sikap dan penampilan, loyalitas), conformity (beda lho antara “conform” dan “confirm”).

Diskusi menarik terjadi pada saat masuk ke bagian pembahasan group cohesiveness, group decision making, dan group process (conflict management, corelation between level of conflict and level of group performance).

Definisi team memiliki arti yang lebih sempit daripada group.

Work Team = A group whose members work intensely on a specific common goal using their positive synergy, individual and mutual accountability, and complementary skills.

Types of Teams
- Problem-solving teams
– Self-managed work teams
– Cross-functional teams
– Virtual teams

Characteristics of Effective Teams
– Have a clear understanding of their goals.
– Have competent members with relevant technical and interpersonal skills.
– Exhibit high mutual trust in the character and integrity of their  members.
– Are unified in their commitment to team goals.
– Have good communication systems.
– Possess effective negotiating skills
– Have appropriate leadership
– Have both internally and externally supportive environments

Ekonomi Teknik [5] October 12, 2008

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Pak Farizal masuk ke pembahasan mengenai Estimating for Economis Analysis. We should give 85% ouf our time and effort to:
– Define the situation
– Estimates cost and benefits
– Determine cash flows
– Determine interest rates, MARR
The rest of 15% to run the numbers.

Estimation is not an easy task and could be wrong. Good estimations have mora than single number. While qualitative method relies on gut feeling and experts’ judgment, then quantitative method includes time series technique and cost engineering techniques.

Untuk project (bobotnya 20% dari keseluruhan penilaian untuk kuliah ini), sebelum tanggal 1 November 2008 setiap mahasiswa harus memilih salah satu dari topik di bawah ini dan menentukan 1-2 bahan referensinya (harus dari jurnal yang diterbitkan sesudah tahun 2003). Setiap topik dipilih oleh maksimal 2 orang mahasiswa:
– Capital budgeting
– Cost of capital or MARR
– Lease-buy decision
– Consideration of multiply objectives and criteria in analysis
– Fuzzy cash flow analysis
– Rate of return method (IRR, ERR)
– Benefit-cost ratio method
– Payback method
– Replacement analysis
– Economic evaluation of advanced manufacturing system
– Energy economics
– Forecasting economic consequences
– Economic stochastic models
– Sensitivity analysis
– Risk analysis
– Inflation
– Government agencies and public utility analysis method
– Cost engineering method

Bisa saja dipilih dari topik selain yang disebutkan di atas, dengan persetujuan Pak Farizal. Selanjutnya bahan tersebut dibuatkan laporan (artikel) sepanjang 10-12 halaman, diserahkan pada tanggal 13 Desember 2008.

Tugas meliputi juga improving on the models presented (or suggest some development) and providing example(s) of the improvement. The least action can be done is applying the models to different numerical examples. Sounds big, doesn’t it?

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