Yes, it's possible to conduct a meta-analysis for a single group in the RevMan program. This type of meta-analysis is often referred to as a "single-arm meta-analysis" or "one-sample meta-analysis." In RevMan, you can perform this type of analysis by treating the data from your single group as if it were the treatment group in a typical meta-analysis comparing two groups.

Here's a basic outline of how to conduct a single-arm meta-analysis in RevMan:

1. **Prepare your data**: Organize your data into the appropriate format for RevMan. This typically involves recording the outcome measure of interest (e.g., mean difference, proportion, etc.) along with measures of variance (e.g., standard deviation, standard error, confidence interval).

2. **Create a new review**: Open RevMan and create a new review project.

3. **Enter study data**: Enter the data for your single group study into RevMan. You can do this by adding a new study and entering the relevant outcome data into the appropriate fields.

4. **Specify comparison groups**: Since you only have one group, you'll need to specify a comparison group for the analysis. You can create a "dummy" comparison group with placeholder data or use data from a control group in a similar study if available.

5. **Perform analysis**: Once you've entered all your data, you can perform the meta-analysis using RevMan's analysis tools. Choose the appropriate statistical model based on the type of outcome data you have (e.g., continuous, binary, etc.).

6. **Interpret results**: Review the results of your meta-analysis, including summary effect estimates, confidence intervals, and measures of heterogeneity. Interpret the findings in the context of your research question and study limitations.

Unfortunately, RevMan's user guide does not specifically address single-arm meta-analyses. However, you can find general instructions for conducting meta-analyses in RevMan in the Cochrane Handbook for Systematic Reviews of Interventions, which provides detailed guidance on using RevMan for various types of analyses. Additionally, you may find tutorials or online resources from the Cochrane Collaboration or other research organizations that offer guidance on conducting meta-analyses in RevMan.