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Metrologi Industri & Kontrol Kualitas#7 Fundamentals of statisticsYusuf UmardaniLab. Metrologi IndustriTeknik Mesin Undip2010Teknik Mesin Undip
StatisticsIlmu pengetahuan yang berhubungan dengan koleksi , tabulasi, analisa, penafsiran dan presentasi data kuantitatifSuatu koleksi data kuantitatif yang menyinggung tentang kelompok utama, khususnya ketika data secara sistematis dikumpulkan dan dibandingkan. Contoh adalah statistik tekanan darah, statistik pertandingan sepakbola dll.
Collection of DataDirect ObservationIndirect ObservationFor quality control purposesMarket research & public opinion pollstersVariablesAttributesQuality characteristics that are measurablee.g. weight measured in gramsQuality characteristics that are classified as either conforming or not conforming to spec.e.g. go/no go gage
DataContinuous DataA variable that is capable of any degree of subdivisione.g. measurement such as kg, meters, liters pascalWeight: 11 kg, 11,33 kg, 11, 3398 kgContinuous data are measureableDiscrete DataVariables that exhibit gapse.g. number of conforming rivets : 0,3 , 5, 10, 96, 4,65Discrete data are countable
Describing the DataThese data are difficult to use and are not effective in describing the datas characteristics
01300054121020021112040310340013012
Frequency distribution
Number nonconformingTabulationFrequency0IIII IIII III131IIII IIII92IIII53IIII44III35I1
Grouped Data
RangeR = 2,575 2,531 = 0,044
Cell IntervalOdd interval : 0,001; 0,07; 0,5 or 3 is recommendedNumber of cellsThe best
Cell Midpoints
Tingkat Proses Rata-rata dan Variabilitas Proses Tingkat Proses Rata-rata : Harga pertengahan dimana karakteristik produk (proses produksi berjalan normal) terdistribusi di harga tersebutVariabilitas Proses : Derajat penyebaran di sekitar pertengahanGambar 5.1
Common CausesSpecial Causes
Ketepatan Proses Acuannya : Daerah ToleransiProses Berketepatan Rendah: Proses yang tidak dikehendaki Akan selalu ada produk yang karakteristiknya di luar toleransi Untuk menjamin kualitas produk diperiksa satu per satuGambar 5.2
Proses Berketepatan Menengah: Proses ini akan menghasilkan produk yang hampir semuanya dianggap baikGambar 5.2
Proses Berketepatan Tinggi: Jika proses diyakini masih berjalan normal, pengukuran cukup dengan sampelGambar 5.2
Gambar 5.5
Analytical Methods of Describing a Collection of dataMeasures of central tendencyMeasures of dispersion
A Measure of central tendencyA numerical value that describes the central position of the data or how the data tend to build up in the centerAverageMedianMode
AverageUngrouped DataGrouped Data
AverageWeighted Average
MedianUngrouped technique3, 4, 5, 6, 8, 8 , 10Grouped technique
ModeMode (Mo) adalah Nilai dgn frekwensi terbesar3,3,4,5,5,5,7 Mo = 522,23,25,30,32,36 Mo = tdk ada105,105,105,107,108,109,109,109,110 Mo = 105 & 1091 Mode disebut unimodal2 mode disebut Binodallebih dari 2 disebut multimodal
Measures of DispersionRange : Selisih nilai terbesar dan terkecilR = XH XLStandar deviasi:
*