ASQ考试模拟题？注册可靠性工程师

alygr

请假给位大侠，这道题怎么解答？
An MBA class project requires your team to estimate the proportion of people that will vote in the next election. You have no prior knowledge of how many are expected to vote. In order to assure an estimate that falls within five percentage points of error, how many people do you and your team have to survey to achieve this estimate with 95% confidence (assume Normal approximation applies)?
答案：385

格物致知

1.96*[0.5*(1-0.5)/N]^0.5≥0.05
N≥384.16
取N=385

alygr

格物致知 发表于 2019-9-5 09:48
1.96*[0.5*(1-0.5)/N]^0.5≥0.05
N≥384.16
取N=385

您好，能再解释下吗？没太看懂

格物致知

alygr 发表于 2019-9-5 11:17
您好，能再解释下吗？没太看懂

假设每个人是否投票概率的为1/2，进行多次调查，就构成二项分布。
均值的置信区间为 x±(Zα/2)*σ/√N
要求95%置信度误差小于5%（within five percentage points of error……with 95% confidence ），则有
1.96*[0.5*(1-0.5)/N]^0.5≤0.05  （上面写错为≥）

alygr

格物致知 发表于 2019-9-5 12:03
假设每个人是否投票概率的为1/2，进行多次调查，就构成二项分布。
均值的置信区间为 x±(Zα/2)*σ/√N
...

好的  谢谢