How is This Data Compiled?

One of the most common questions received is how the information provided about what different denominations believe is collected. That is very fair, as information is only worthwhile to the extent it is true and trustworthy.

Providing trustworthy and useful information is one of the highest priorities of this site. While certainly errors will happen, items are not added without some level of verification. This rigor does lead to a slower pace of adding new content and causes many blank spaces, especially towards the bottom of the table. However, untrustworthy information is worse than no information at all.

The process of adding information is tiered, going down the list until the information is found or the search is exhausted:

The ideal situation is in situations where the denomination has a hierarchical structure and a statement is made by the leader of the entire denomination. This is the most authoritative source of information. This would look like the Vatican, Mormon President, or Seventh-day Adventist General Conference making a statement. Even the World Methodist Council or World Communion of Reformed Churches are generally considered authoritative as they represent a very large portion of their denominations.
If the denomination is more fractured or if the governing body does not have a statement regarding a belief, statements are sought from larger sub-denominations or regional bodies. For Pentecostalism, this mainly means the Assemblies of God's doctrine. For Methodism, beliefs can be compared between the United Methodist Church, Church of the Nazarene, Global Methodist Church, Wesleyan Church, etc. For Anglicanism, the Church of England, Episcopal Church, Church of Ireland, etc. can be compared. For Oriental Orthodoxy, the Ethiopian Orthodox Tewahedo Church, Coptic Orthodox Church, Syriac Orthodox Church, etc. can be compared. This works okay, but it is quite prone to bias towards English-speaking and tech-savvy denominations, though it does at least ensure that a sizable portion of the denomination is represented.
If no denominations or sub-denominations have a statement, then statements from individual churches are sought. This gets quite prone to error, as individual churches can be quite different from the denomination as a whole and it is hard to get a representative sample. However, if churches seem to be in agreement, it is generally safe to assume that it is a fairly common belief.
If no churches have such doctrinal beliefs listed, then theoretically surveys of individuals can be used. In practice, this is not that useful as it is hard to get a large sample size, and individuals' beliefs and what denomination they identify as can vary wildly from the denomination's official beliefs. It may be useful when a large enough sample size is obtained and good agreement is found, but this is quite rare.

Regardless of where information comes from, citations are added whenever possible to allow for verification.

It is not uncommon to get complaints that the provided info of a denomination's beliefs do not line up with with what a member of that denomination believes. On one hand, it is never the intention to misconstrue anyone's beliefs. The goal is always to be as accurate as possible. On the other hand, you will never get everyone in a denomination to agree on anything, and just saying "it varies" on everything undermines any descriptive utility. Some generalization is necessary to actually provide any information. If there is notable disagreement, that should be noted by at least saying "most believe" something, but just understand that just because something is representative of a denomination's beliefs does not mean that every single member believes that thing. This site provides a good overview of beliefs, but it is not a replacement for actually talking to people.