In a previous thread I outlined a study in which we measured the heart rate of embryos exposed to a drug at different graded pH levels. Heart rate and pH were measured before incubation, and after 1h incubation.
In this part of the experiment, heart rate and pH were measured each hour over a 3h incubation period, that is at 0h, 1h, 2h, and 3h. Except pH was not measured at time=2h. This means that when I run -mixed- with measured pH as a covariate, the adjusted heart rate at 2h is not calculated.
What is the best practice for filling in missing data like this?
I have been looking at -hotdeck- as one possibility, but have read that
To give you an overview of the data, we essentially have three groups: those exposed to 0mM drug and 17.9mM NaHCO3 (neutral pH); those exposed to 6mM drug and 23.8mM NaHCO3 (neutral pH); and those exposed to 6mM drug and 16.1mM NaHCO3 (pH acidic by 0.2 units). Heart rate is given below:

And pH:

The value of pH at 2h could probably be estimated as the mean of 1h and 3h values, but am I introducing my own bias here? It could just as easily be the same as the value at 3h (i.e. linear reduc
The data in wide and long format are given in the next posts.
In this part of the experiment, heart rate and pH were measured each hour over a 3h incubation period, that is at 0h, 1h, 2h, and 3h. Except pH was not measured at time=2h. This means that when I run -mixed- with measured pH as a covariate, the adjusted heart rate at 2h is not calculated.
What is the best practice for filling in missing data like this?
I have been looking at -hotdeck- as one possibility, but have read that
There are more elaborate methods that ^only^ replace missing values, rather than the whole row, for imputed values.
And pH:
The value of pH at 2h could probably be estimated as the mean of 1h and 3h values, but am I introducing my own bias here? It could just as easily be the same as the value at 3h (i.e. linear reduc
The data in wide and long format are given in the next posts.
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