There are couple of ways to deal with missing data.

• Replace missing values by mean/median. If the missing values is very less, then this method would be apt. Also depends on how much skewed your data is.
• Imputation. Build a linear regression model to predict the missing values based on other parameters. KNN could also be used to predict the missing value

Also there are other methods to deal with missing data such as mimicing the parameters, removing missing data, etc.

There are couple of ways to deal with missing data.

• Replace missing values by mean/median. If the missing values is very less, then this method would be apt. Also depends on how skewed your data is.
• Imputation. Build a linear regression model to predict the missing values based on other parameters. KNN could also be used to predict the missing value

Also there are other methods to deal with missing data such as mimicking the parameters, removing missing data, etc.