Pedometers have become a frequently used tool to measure physical activity. The accuracy of pedometers has been an interest of many researchers given the popularity of the tool. When, pedometers are employed, there are many potential sources of error, including missing data. Because previous studies indicated that the amount of missing data does not alter the strength of the relationship between PA levels and relevant health outcome variables, some researchers argued that the missing data may not be a significant concern. In a public health perspective, previous researchers’ point of view may be true. This missing data, however, can be a significant problem if researchers are interested in directly comparing between groups and/or conditions. Without knowing how much information is missing, it is impossible to make direct comparisons. Therefore, the purpose of the study is to examine how much information is missed when participants are asked to follow the common instructions of pedometer daily wear.