A department store manager is interested in determining the mean number of days that employees will take to learn the location of all products in the store. If past training records show a standard deviation of 9 days, what sample size should be used so that, at 95% confidence, the margin of error will be 3 days

At the beginning of a call to the cable company, a message tells customers, "after you finish talking to our customer service representative, you will be asked to take a five-question survey about the level of service you recieved. it would be appreciated if you could stay on the line to answer the survey questions." what type of sampling is the cable company using?