Chúng tôi gần đúng các dải đại diện hình thang. Đối với một bản vẽ rõ ràng hơn, chỉ có năm dải được sử dụng. Rõ ràng hơn, nhỏ hơn, dải cần thiết cho một xấp xỉ tốt. Hãy để có được dải n và do đó n + 1 điểm dữ liệu. Diện tích một dải điển hình là | 286 A Guide to Microsoft Excel 2002for Scientists and Engineers A B I c D El F I G h F J 1 K 1 Paired sets 2 Data Calculations t-Test Paired Two Sample for Means 3 Sample A B diff mean diff 4 1 1 n 6 A B 5 2 SSD Mean 6 3 st dev Variance 7 4 t expt Observations 6 6 8 5 alpha Pearson Correlation 9 6 4 23 0 35 t critical Hypoth Mean Diff 0 10 decision same df 5 11 t Statistic 12 P T t one-tail 0 211 13 p apprcacF t Critical one-tail 14 p from t-test P T t two-tail 0 423 15 1 Critical two-tail Figure a On Sheetó of enter the text values shown in columns A G of Figure . For now ignore columns I K. Enter the values shown in A4 C9. b Enter the formula B4 C4 in D4 and copy it down to row 9. c The formulas in column G are G3 G4 G5 G6 G7 G8 G9 GIO GI4 AVERAGE D4 D9 COUNT A4 A9 DEVSQ D4 D9 SQRT G5 G4-1 G3 SQRT G4 G6 TINV G8 G4-1 IF G7 G9 same not same TTEST B4 B9 04 09 2 1 Computes the p-value Computes d Computes n Computes fd -df Computes Sj Compute experimental The required a-value Computes critical We are led to the conclusion that the two methods give the same mean with an a-value of since i experimental is less than t critical and ii the p-value computed by TTEST is greater than the alpha value or . To round off this exercise we use the t-TEST Paired Two Sample for Means tool from the Data Analysis tool. This is left as an exercise for the reader. Note that you should set the Hypothesized mean difference to 0 and the alpha value to when completing the tool s dialog box. The results are shown in the figure. As expected the results agree with our own calculations. The experimental values in G9 and J1 5 are the same as are the p-values in G14 and J14. These serve as useful checks but recall that the results from the tool are static whereas our calculations will be .
