4. The purpose of the investigation was to examine the effects of the Tweed
edgewise technique on mandibular growth and rotation. It employed 36 Class II
Tweed edgewise patients, all of whom had 4 bicuspids extracted during the course
of treatment. Pre-treatment (time 1), post-treatment (time 2) and post-retention
(time 3) records of these patients were matched by age, gender, malocclusion,
and treatment interval to untreated controls from the Bolton-Brush Growth Study
Center, Cleveland. The cephalograms of the two samples were traced, digitized
and analyzed by descriptive cephalometric analysis. Analysis was directed
toward an analysis of the increments of change (for various cephalometric
measurements) between time 1 and time 2, time 2 and time 3, and, overall,
between time 1 and time 3. The table below has the results of the paired t-tests
comparing the amount of change (between time 2 and time 3) in 3 cephalometric
measurements in the treated group vs the controls. Please interpret the results
Groups Paired t-test
Variable
ANB -0.4 0.1 0.0 0.1 0.4 0.2 -1.7
Co-Gn 3.2 0.4 1.4 0.4 1.8 0.5 3.8**
Overjet 0.4 0.2 -0.4 0.2 0.7 0.2 3.3**
*p<0.05; **p<0.01
Treated Control Difference t-value Mean SD Mean SD Mean SD
To interpret the results of the paired t-tests comparing the amount of change in cephalometric measurements between the treated group and the control group, you need to focus on the t-values and the p-values indicated in the table.
1. The t-value is a statistical measure that quantifies the difference between the means of two groups. Higher absolute t-values indicate larger differences between the groups.
2. The p-value represents the probability of obtaining the observed results if the null hypothesis were true. Typically, a p-value less than 0.05 is considered statistically significant, indicating that the observed differences are unlikely to have occurred by chance.
Looking at the table, we see three variables being compared: ANB, Co-Gn, and Overjet.
For the ANB variable, the t-value is -1.7. Since the absolute value of the t-value is less than 2 and the p-value is not provided, we cannot make any definitive conclusions about the difference in ANB between the two groups.
For the Co-Gn variable, the t-value is 3.8, and there is a double asterisk (**). This indicates that the p-value is less than 0.01, which means there is a statistically significant difference in Co-Gn between the treated and control groups.
For the Overjet variable, the t-value is 3.3, also with a double asterisk (**), suggesting a p-value less than 0.01. This indicates a statistically significant difference in Overjet between the treated and control groups.
In conclusion, while there is no significant difference in ANB between the groups, the Co-Gn and Overjet variables show statistically significant differences between the treated and control groups.