Practical Solutions Analysing Continuous Data

2 1)To produce the overall histogram you can use the options exactly as given. This results in the following syntax: To split the graphs by treatment group, the easiest way is to add the group variable to the Panel By:  Rows box. This results in the following syntax: * Producing the overall histogram. GRAPH /HISTOGRAM(NORMAL)=HBA1CRED /TITLE= 'Overall Histogram of blood sugar reduction'. * Producing the histograms split by group. GRAPH /HISTOGRAM(NORMAL)=HBA1CRED /PANEL ROWVAR=GROUP ROWOP=CROSS /TITLE= 'Histograms of blood sugar reduction, by group'. Practical Solutions

3 1)The histograms do not look highly skewed (although the individual group histograms show some skew) and the combined histogram actually appears to follow a normal distribution very well. There may be an outlier in the Active A group. Practical Solutions

4 2)Along with the observed mean difference, its confidence interval and the p value should be reported. The mean difference between the starting HbA1c level and 7 is 0.13 (95% CI: -0.06, 0.32). The starting HbA1c level is not statistically significantly different from 7 (p=0.168). (NOTE: The CI also includes 0) Practical Solutions

5 3)For the non-parametric test there is only a p value to report from the test (although the median could be reported from elsewhere and a CI could be calculated from CIA). The starting HbA1c level is not statistically significantly different from 7 (p=0.253). Practical Solutions

6 4)(i) Along with the observed mean HbA1c difference, its confidence interval and the p value should be reported. The mean difference in HbA1c levels is 1.05 (95% CI: 0.94, 1.17). There is a highly significant decrease in the levels of HbA1c between the two readings (p<0.001). Practical Solutions

7 4)(ii) Along with the observed mean HbA1c difference, its confidence interval and the p value should be reported. The mean reduction in Hb1Ac levels is 1.05 (95% CI: 0.94, 1.17). There is a highly significant decrease in the levels of HbA1c between the two readings (p<0.001). (This is identical to the result from part i) Practical Solutions

8 5)(i) For the non-parametric test there is only a p value to report from the test (although the medians could be reported from elsewhere and a CI for the difference could be calculated from CIA). There is a highly significant difference in the levels of HbA1c between the two readings (p<0.001), with the initial values being significantly higher. Practical Solutions

9 5)(ii) For the non-parametric test there is only a p value to report from the test (although the medians could be reported from elsewhere and a CI for the difference could be calculated from CIA). There is a highly significant difference in the levels of HbA1c between the two readings (p<0.001), with the initial values significantly higher. (This is identical to the result from part i) Practical Solutions

10 6)(i) Along with the observed group means for the final HbA1c, the mean difference, its confidence interval and the p value should be reported. There is a mean difference of 0.29 (95% CI: -0.24, 0.82) between Active A and B, with Active B having the larger final HbA1c. This small difference however is not statistically significant (p=0.276). (The SD’s are similar  Use equal variances version) Practical Solutions

11 6)Shown below is one way of tabulating these results: Practical Solutions Table 1: Comparison between Active treatments OutcomeActive AActive B Active B – Active A Mean difference (95% CI) P value Blood sugar reduction mean (SD)5.72 (1.80)6.01 (1.61)0.29 (-0.24, 0.82)0.276 min to max1.36 to to 9.88 n8380

12 6)(ii) Along with the observed group means for the final HbA1c, the mean difference, its confidence interval and the p value should be reported. There is a mean difference of 0.79 (95% CI: 0.27, 1.31) between Active A and Placebo, with Placebo having the larger final HbA1c. This difference is highly statistically significant (p=0.003). (The SD’s are similar  Use equal variances version) Practical Solutions

13 7)(i) For the non-parametric test, again, there is only a p value to report from the test (although the group medians could be reported from elsewhere and a CI for the difference could be calculated from CIA). The final HbA1c level for the Active A and Active B groups does not show a statistically significant difference (p=0.346), although the active B group had slightly higher values. Practical Solutions

14 7)(ii) For the non-parametric test, again, there is only a p value to report from the test (although the group medians could be reported from elsewhere and a CI for the difference could be calculated from CIA). The final HbA1c level for the Active A and Placebo groups shows a highly statistically significant difference (p=0.004), with the Placebo group having significantly higher values. Practical Solutions