When a study involves a test about a mean, data should always be scrutinized for possible outliers or heavily skewed
data. The $t$ test and the $t$ interval rely on certain assumptions. Which of the given statements is true?
The most important aspect for validity is a simple random sample from the population of interest.
All of the answer options are correct.
As long as the sample size is at least 15 and there are no outliers among the data, we can use a $t$ test.
As long as the sample size is at least 40, we can use the $t$ test even if the data exhibits skewness.