We estimate a parameter $\phi$ and get a measurement value of 20.35.

Which of the following (mark one) is a correct $95\%$ confidence interval for $\phi$ ? We assume that we know that the standard deviation of the measurement is $\sigma$ .

☐ $[20.35 - q_{0.975}\sigma, \quad 20.35 + q_{0.975}\sigma]$

☐ $[\phi - 20.35 \cdot q_{0.975}\sigma, \quad \phi + 20.35 \cdot q_{0.975}\sigma]$

☐ $[20.35 - \phi \cdot q_{0.975}\sigma, \quad 20.35 + \phi \cdot q_{0.975}\sigma]$

☐ $[q_{0.975}\sigma - 20.35, \quad q_{0.975}\sigma + 20.35]$

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