1.) The weekly mean income of a group of executives is $998 and the standard deviation of this group is $99. The distribution is normal. What percent of the executives have an income of $908 or less?
2.) A random sample of 90 group leaders and supervisors revealed that they worked an average of 6.8 years before being promoted. The population standard deviation was 1.9 years. Using the 0.95 degree of confidence, what is the confidence interval for the population mean?