U is besig om ʼn ondersoek te doen om die gemiddelde inkomste van gesinne in die Noord-Kaap vas te stel. Uit ʼn voorafgaande steekproef weet u dat die standaardafwyking van inkomste van gesinne R500 is. Die borg van die ondersoek wil ʼn vertrouensvlak van 95% gebruik en u beramer moet binne ’n interval van R200 wees. Met hoeveel families moet u onderhoude voer? / You are to conduct a sample survey to determine the mean family income in the Northern Cape. From a previous sample of 10 families, the standard deviation of the income of families is known to be R500. The sponsor of the survey wants you to use the 95% confidence level. The estimate is to be within an interval of R200. How many families should be interviewed?