A student went to the local county courthouse (in Cumberland County, Pennsylvania, in June and July of 1993) to gather data on ages of soon-to-be husbands and wives who had recently applied for marriage licenses. He gathered age data on a sample of 100 couples and calculated the difference in age (husband – wife) for each couple. Do you consider it valid to use a theory-based confidence interval for a population mean, based on these sample data?