Final answer:
When we construct a 90 percent confidence interval, it means that we are 90 percent confident that the true population mean lies within the interval.
Step-by-step explanation:
When we construct a 90 percent confidence interval, it means that we are 90 percent confident that the true population mean lies within the interval. In other words, if we were to take repeated samples and construct 90 percent confidence intervals from each sample, we would expect 90 percent of those intervals to contain the true population mean.