Anational firm reports mean earnings of $75 ± $12 (µ ± σ) per unit sold over the lifetime of the company. a competing company over the past 36 reporting periods had reported mean earnings equal to $78 per unit sold. conduct a one-sample z test to determine whether mean earnings (in dollars per unit) are larger (compared to that reported by the national firm) at a .05 level of significance. 1. state the value of the test statistic and whether to retain or reject the null hypothesis. 2. compute effect size using cohen’s d.