使用量具A 和B 去测量同批16个部件，数据如下，请问在检验均值是否存在差异的假设检验中的自由度应该是多少？
量具A 量具B
样本均值94.49 94.38
样本标准差27.71 27.69（）

以下为单因子随机试验结果，三台机器（A，B，C）的结果如下：A B C42-380151-272-1640请问：误差项的平方和等于多少？（）

A.170
B.130
C.28.8
D.14

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Contributions to a Roth IRA:I.May be rolled-over from a regular IRA in a nontaxable transaction.II.May be tax deductible.III.Are not taxed when withdrawn if they have been in an established account for at least five years and the taxpayer is at least 591 2 before withdrawals are made.().A、Only statement I is correctB、Only statement II is correctC、Only statement III is correctD、Statements I, II, and III are correct 点击查看答案