Appropriate Measures of Central Tendency

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Appropriate Measures of Central Tendency

• Nominal variables Mode
• Ordinal variables Median
• Interval level variables Mean
• - If the distribution is normal (median is
  better with skewed distribution)

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Central tendency and the shape of the
distribution
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Ukuran Penyebaran

• Suatu data yang mempunyai kecenderungan
  (tendensi) pusat misalnya rata-rata yang sama
  belum tentu mempunyai penyebaran data yang sama
  pula.
• Ukuran penyebaran (variasi) menyatakan seberapa
  jauh nilai amatan yang sebenarnya menyimpang atau
  berbeda dengan nilai pusatnya.
• kegunaan dari ukuran variasi ini untuk
  mengetahui seberapa jauh observasi melenceng dari
  nilai rata-ratanya.

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• How well does the mean represent the scores in a
  distribution? The logic here is to determine how
  much spread is in the scores.
• How much do the scores "deviate" from the mean?
  Think of the mean as the true score or as your
  best guess.
• If every X were very close to the Mean, the mean
  would be a very good predictor.
• If the distribution is very sharply peaked then
  the mean is a good measure of central tendency
  and if you were to use the mean to make
  predictions you would be right or close much of
  the time.

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• The larger the standard deviation figure, the
  wider the range of distribution away from the
  measure of central tendency

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Ukuran-Ukuran Penyebaran

• Range (Jangkauan)
• Merupakan selisih nilai observasi tertinggi
  dengan nilai observasi terendah.
• Contoh

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Variansi

• Variansi populasi

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• Contoh
• Tentukan variansi dari 5, 7, 2, 2, 4 !
• Peny
• Rata-rata 5
• Variansi 4.5