题目
The height of a certain species of plant is denoted by . The heights of a random sample of plants were measured, and the following results were found.
- The mean, , for the sample was .
- An unbiased estimate of the population variance of was .
Calculate the value of .
题目中文翻译
某种植物的高度记为 。随机抽取 株植物,测量其高度,得到下列结果。
- 样本均值 为 。
- 的总体方差的一个无偏估计值为 。
计算 的值。
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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反用无偏方差公式,把已知的样本均值与方差代入,再解出平方和。
答题过程
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Using ,
Therefore