The valid per cent is simply the proportion of a sample that is valid. Data can be invalid for a variety of reasons. Some data are simply impossible, such as negative heights or weights. Some data can be shown to be invalid by comparing them with other data. For example, a person might be two years old, and a person might be a widow. But it is hard to conceive of a person who is a two year old widow! Finally, some data can be identified as machine error or data entry error.

- Skill level:
- Easy

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## Instructions

- 1
Write down the total sample size. For example, you might have 1000 cases.

- 2
Write down the number that are invalid. For example, there might be 92 invalid cases for one reason or another.

- 3
Subtract the result in step 2 from that in step 1. For instance 1000 - 92 = 908.

- 4
Divide the result in step 3 by the result in step 1 and multiply by 100. 908/1000 = .908. .908*100 = 90.8. Therefore 90.8 per cent of our data are valid.