题目
Anil is a candidate in an election. He received 40% of the votes. A random sample of 120 voters is chosen.
Use an approximation to find the probability that, of the 120 voters, between 36 and 54 inclusive voted for Anil.
题目中文翻译
Anil 是一场选举中的候选人,他获得了 40% 的选票。随机抽取 120 名选民作为样本。
用近似方法求这 120 名选民中有 36 至 54 人(包括 36 和 54)投票支持 Anil 的概率。
原卷通用作答要求
Answer all questions. You should use a calculator where appropriate.
You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.
Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.
请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。
解答
解法一
思路
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投票人数服从二项分布,含端点36至54的连续性修正是35.5至54.5。
答题过程
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Let . Since and are both greater than 5, use .
With continuity corrections,