A technician working for the Chase-National Food Additive Company would like to estimate the preserving ability of a new additive

A technician working for the Chase-National Food Additive Company would like to estimate the preserving ability of a new additive. This additive will be used for Auntie’s brand preserves. Based on past tests, it is believed that the time to spoilage for this additive has a standard deviation of 8 days. To be 95% confident of the true mean time to spoilage, what sample size will be needed to estimate the mean time to spoilage with an accuracy of one day?