NHIS moderate physical activity (NIU issue)


To create a variable for minutes of moderate physical activity per week, I multiplied MOD10DMIN by MOD10FWK. However, I am running into a problem with people who never exercise (code 95 for MOD10FWK). Are those individuals included in the NIU (code 0) for MOD10DMIN? When analyzing the datam MOD10DMIN has a higher number of missing values compared to MOD10FWK. Further analysis reveals that a great number of those who say they never exercise (MOD10FWK) are also NIU for MOD10DMIN.



Yes, if MOD10FWK==95, then it is the case that the respondent never participated in moderate activity of at least 10 minutes in a week. As such, given the universe statement for MOD10DMIN, they will be NIU in MOD10DMIN.

Since there are different universe statements for MOD10FWK and MOD10DMIN, the total number of NIU for each will not be the same.