Which of the Following Cases Require the Mean of a Sample

Multiple Choice

Which of the following cases require the mean of a sample to be calculated using the formula $\bar { x } = \frac { \sum _ { i = 1 } ^ { N } f _ { i } x _ { i } } { N }$ , where N represents the sample size?

A) the sample has no mode value
B) there is direct access to the raw data
C) sample data are grouped in a frequency distribution
D) the coefficient of skewness is 1 or less than -1