Suppose that you want to project a vector of data (x1,x2,x3,...,xn) into the one dimensional subspace generated by the vector (1,1,...,1). What's the projection

Suppose that you want to project a vector of data (x1,x2,x3,...,xn) into the one dimensional subspace generated by the vector (1,1,...,1). What's the projection in this case? Hint: You obtain the most important concept of statistics.