在对密码的统计攻击中，可用已知语言的各双字母组的频度来攻破密码。
In statistical attacks on ciphers the known frequency of various bigrams, in a given language, can be used in attempts to break the cipher.
少儿组的症状与青年组比较，其中17项症状频度有极显著性差异（P＜0．01）。
There were significant differences in the 17 symptoms between the childhood groups and young groups ( P< 0 01).
患者病前生活事件频度明显高于健康组。
Results also indicated a higher frequency of life event experienced before the onset of disesaethan that of healthy controls.
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