Sample size: determine the sample size needed to estimate the density of a new asphalt mix with a precision of 4.0 kg m-3 if the population standard deviation is unknown and the sample standard deviation is assumed to be 8.0 kg m-3 . use a significance level of 0.02. a. what is the confidence level? b. what sample size is estimated using the z distribution? can the z distribution be used? should the t distribution be used? explain. c. what sample size is estimated using the t distribution? document your work in a table, with sample calculations shown below the table.