During the laying of gas pipelines, the depth of the pipeline (in \(\mathrm{mm}\) ) must be controlled. One service provider recorded depths of
\[\begin{array}{lllllll}418 & 428 & 431 & 420 & 412 & 425 & 423 \\ 433 & 417 & 420 & 410 & 431 & 429 & 425\end{array}\]
(a) Find the sample mean.
(b) Find the sample standard deviation.
(c) Find the coefficient of variation.
(d) Measurements by another service provider have a sample mean of 425 and standard deviation of 6.36. Which provider's set of measurements is relatively more variable?