An example of why we must ALWAYS check the image.

Digging thru Riddles in the Warren Co TN area I was reminded of why you should always click thru to the image for further examination.

Reading the index would make you think this household is made up of 2 Males.  That really doesn't make sense given that the head of household is female.  Even if she were a person of color she would be listed in Total All column.

I pasted the column headers in just above the snippet of Mary's entry so you could see how many in each age group and gender were enumerated. (Click image to enlarge)

The index did not include the 3 white females in the household.  

1 ------- 30-under 40

1 ------- 50-under 60

1 ------- 70-under 80

I left a comment on this entry to make others aware of the omission.  

When you think about how many people this information has passed thru it's amazing that we still have any of it.

This particular entry was from the Ancestry Database of the 1830 United States Federal Census.  That database was made using images digitized by FamilySearch of the census pages which were microfilmed by the NARA.  I do not know who indexed the census. Those pages of census data were collected by the census taker from someone in that household(and in some cases probably a neighbor).  From what I understand it was not uncommon for the census taker to collect the data and then write it on the census form later in his best...or sometimes worst handwriting.  I checked to see if the 1830 census pages still exist but from what I can gather the NARA only has the negative photostatic copies for the year 1830. [1]

Ancestry Database:
Ancestry.com. 1830 United States Federal Census [database on-line]. Provo, UT, USA: Ancestry.com Operations, Inc., 2010. Images reproduced by FamilySearch.1830; Image 141 of 158.

Family History Library Film:
Census Place: Warren, Tennessee; Series: M19; Roll: 181; Page: 367; Family History Library Film: 0024539

Original data: 

Fifth Census of the United States, 1830. (NARA microfilm publication M19, 201 rolls). Records of the Bureau of the Census, Record Group 29. National Archives, Washington, D.C.