Key Concepts about Missing Physical Activity Monitor Data

For our physical activity monitor analysis, we will assess outcomes for study participants whose monitors were calibrated throughout the study period, who had data deemed reliable, and who had 10080 data points representing each minute of the week-long study period. In the previous section of the tutorial, we identified study participants who met these criteria and those who did not.  For study participants who did not, we classify their data as missing.

Missing values may distort the results of your analysis. You must evaluate the extent of missing data in your dataset to determine whether the data are useable without additional re-weighting for item non-response. As a general rule, if 10% or less of your data for a variable are missing from your analytic dataset, it is usually acceptable to continue your analysis without further evaluation or adjustment.

Later in the tutorial, we select a subset of study participants for our analysis based on the number of valid days measured by the physical activity monitor. As an analyst, you may choose to describe the population of study participants who do not meet the criteria for number of valid days or you may choose to further adjust your analysis as needed.