Read this article. How do you think the questions in this section would be answered?
Do I have representative testimonies?
More does not necessarily mean better. You might want to have a reasonable sample of testimonies to determine patterns. At the same time, there is some value to interviewing just one or a few eyewitnesses. For example, if dozens of protesters witnessed a human rights violation during a strike, you might not need to interview every striker because their version of the events are similar; however, you would want to interview any police or security forces present to record their version of the event.
The writer interviewed protesters and people involved in the rally. These witnesses would be biased against the police who are trying to stop the demonstration. Since the author interviewed only demonstrators, the article lacks a diversity of opinions. In this case, the author would have gotten other points of views if she had interviewed bystanders and/or the police. In this case, the author is interviewing people as the demonstration happens, this means the testimonies are “fresh” and add to the article’s credibility. The number of testimonies is enough to get a sense of what happened. However, as previously mentioned, the article would benefit from more representative testimonies of other people involved in the rally (police, bystanders, etc.).