Kristen Ashford purchased the subscribers list for Wind Surfing magazine. She plans to survey a sample of the subscribers before using the list in her mail order business. The names are numbered consecutively from 1 to 5,000. Kristen chooses her sample by selecting four-digit numbers (1 to 5,000) from a random number table. Her sample is a O simple random sample O stratified sample O systematic sample O convenience sample O cluster sample