The formula to determine how much the sample size is suitable for research
There are two formulas to determine sample size. The size of the sample applied in the study are based on demand of factor analysis to discover EFA (Exploratory Factor Analysis) and regression:
For exploring factor analysis EFA: Based on research by Hair, Anderson, Tatham and Black (1998) to refer to the planned sample size. Minimum sample size is 5x(number of observe variables). This is the appropriate sample size for studies using factor analysis (Comrey, 1973; Roger, 2006). n = 5 * m, note that m is the number of questions in all.
For multivariate regression analysis: the minimum sample size to be achieved by the formula is n = 50 + 8 * m (m: number of independent variables) (Tabachnick and Fidell, 1996). Note m is the number of independent factors, rather than the question of independence.
Therefore, when choosing the number of samples must meet both of the above formula.