Can you provide additional information, such as the number, and just as importantly the type, of the other variables in the data? If you are trying to predict a continuous variable from data which is predominantly categorical, and also subject to missingness, you may not have enough complete cases to predict the continuous variable.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.