7.t-Test: Paired Two Sample for MeansVariable 1Variable2Mean13.6433333311.92167Variance37.481666679.347137Observations66Pearson Correlation0.977638859Hypothesized Mean Difference0df5t Stat1.318467853P(T<=t) one-tail0.122254948t Critical one-tail2.015048373P(T<=t) two-tail0.244509897t Critical two-tail2.570581836As shown with the t-test, the tcalculatedis 1.3185 which is less than 2.57058 meaning that the meansare not too different.8. external method uses know quantities of the analyte to get absorption. A graph is drawn and the concentration of the unknown is found by using the equation of the line. For standard addition, a known quantity is added to the unknown and for the Internal method, a known amount of the compound is added, this compound should be different from the analyte. From there the concentration of the unknown can be found.