I am trying to interpret these 2 residual vs fitted value plots if anyone can help. I was reading about a cone like structure (heteroskedasticity) but am unsure if this is the case in the first one. Obviously this isnt great but i cant pinpoint what its telling me. The same in the second plot, this is really bad, i think it's saying that my upper and lower values are poor but would be good if someone could confirm.
The plots indicate that the model suffers from heteroscedasticity. Generally, any systematic patterns (like a cone shape in the first plot or an inverted-U shape pattern in the second plot) may indicate the presence of heteroscedasticity. The error variance does not seem to be constant, meaning your regression results may not be reliable.
But, it's better not to rely on just graphs. You should try formal tests of heteroscedasticity to make sure.
If you find that heteroscedasticity exists (using formal tests), try applying Robust Standard Errors in your regression model. Then, compare its results with your original model. If the significance of variables does not change, heteroscedasticity is not a serious problem in your model. But if variable significance changes, you cannot rely on your model.