Answer:
(a) 31 , 54
(b) 48
Explanation:
(a) Locator: 0.2*30 = 6
  Round up to 7
  20% decile = 31
  Locator: 0.8*30 = 24
  Round up to 25
  80% decile = 54
(b) To determine 67th percentile
  Locator : 0.67^30 = 20.1
  Round up to 22
  67% percentile = 48
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