Question

ch 20* because the t procedures are robust, the most important condition for their safe use is that the population distribution is exactly normal. the data can be regarded as an srs from the population. the population standard deviation σ is known.

Explanation:

• For the first option: \(t\) - procedures are robust, which means they don't require the population distribution to be exactly normal. A moderate departure from normality doesn't severely affect the performance of \(t\) - tests and \(t\) - intervals.
• For the second option: Simple Random Sampling (SRS) is crucial. The \(t\) - procedures are based on the assumption that the data is collected in a way that each sample of a given size has an equal chance of being selected from the population. This helps in generalizing the results from the sample to the population.
• For the third option: In \(t\) - procedures, the population standard deviation \(\sigma\) is unknown (if \(\sigma\) were known, we would use \(z\) - procedures). We estimate the standard deviation using the sample standard deviation \(s\).

Answer:

the data can be regarded as an SRS from the population.