Mahbooben, It all depends. If you are comparing only one factor, one-way would do; if two factors, two-way ANOVA needs to be used. There is a 3-way ANOVA also, but then it starts becoming complicated with multiple factors..
I agree with both Ben Porter and Pradeep Kumar Naik: choosing between one-way and two-way anova has nothing to do with whether the data are balanced or not.
I would also mention that you should check on how your software handles unbalanced data in anova. Good software will handle unbalanced data in anova without difficultly.
1. It is depend on your data, how many random variables.
2. What is the relation between the random variables, i.e related or not.
3. One way ANOVA:
The unrelated/uncorrelated analysis of variance indicates whether several (two or more) groups of scores have very different means. It assumes that each of the sets of scores comes from different individuals. It is not essential to have equal numbers of scores for each set of scores.
The different groups correspond to the independent variable. The scores correspond to the dependent variable.
Basically the analysis of variance calculates the variation between scores and the variation between the sample means. Both of these can be used to estimate the variation in the population. If between samples variation is much bigger, it means that the variation due to the independent variable is greater than could be expected on the basis of the variation between scores. If this disparity is big enough, the difference in variability is statistically significant. This means that the independent variable is having an effect on the scores.
4. Two way ANOVA:
Two-way analysis of variance allows you to compare the means of a dependent variable when there are two independent variables.
If you have more than one dependent variable then you simply repeat the analysis for each dependent variable separately. On the other hand, if the several dependent variables are measuring much the same thing then they could be combined into a single overall measure.
It depends on your variables. In one way ANOVA the researcher takes only one factor. As against, in the case of two-way ANOVA, the researcher investigates two factors concurrently. Please look at the table for differences between One-Way ANOVA and Two-Way ANOVA!