an environmentalist would like to estimate the true mean weight of all cars. to do so, she selects a random…

Explanation:

Step1: Recall margin - of - error formula

The margin of error $E$ for a confidence interval of the population mean (when the population standard deviation $\sigma$ is known) is $E = z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$, where $z_{\alpha/2}$ is the z - score corresponding to the level of confidence, $\sigma$ is the population standard deviation and $n$ is the sample size.

Step2: Analyze each option

• Selecting another sample: Just selecting another sample of the same size and same confidence level does not systematically increase the margin of error. It may change the margin of error randomly depending on the sample values.
• Increasing the sample size $n$: From the formula $E = z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$, as $n$ increases, the value of $\frac{\sigma}{\sqrt{n}}$ decreases, so the margin of error $E$ decreases.
• Increasing the confidence level: As the confidence level increases, the value of $z_{\alpha/2}$ increases. For example, for a 90% confidence level, $z_{\alpha/2}=1.645$, for a 95% confidence level, $z_{\alpha/2} = 1.96$, for a 99% confidence level, $z_{\alpha/2}=2.576$. Since $E = z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$, an increase in $z_{\alpha/2}$ will increase the margin of error.
• Decreasing the confidence level: As the confidence level decreases, the value of $z_{\alpha/2}$ decreases, and thus the margin of error $E$ decreases.

Answer:

increasing the confidence level