同等劑量的藥品采用不同的服用方式往往取得不同的效果，方案A是在每日三餐后服用，方案B是每日僅僅服用一次相同總劑量的藥品。對病情相似的20-44歲的患者進行隨機抽樣，測試所服藥品在消化道中的中轉(zhuǎn)時間，選擇服用方案的順序是隨機的。下表給出了12名患者分別按方案A和方案B服用后，藥品在消化道中的中轉(zhuǎn)時間。
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The number of class intervals in a frequency distribution is usually between （）.
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變量數(shù)列中，各組頻率之和應(yīng)（）
Which of the following is best to show the percentage of a total budget that is spent on each category of items？（）
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