Preventing fatigue crack propagation in aircraft structures is an important element of aircraft safety. An engineering study to investigate fatigue crack in n  9 cyclically loaded wing boxes reported the following crack lengths (in mm):

2.13, 2.96, 3.02, 1.82, 1.15, 1.37, 2.04, 2.47, 2.60.

(a) Calculate the sample mean.

(b) Calculate the sample variance and sample standard deviation.

(c) Prepare a dot diagram of the data.