Refer to the figure below.
Assume that there are n correct measurements

Because each measurement has an error of 0.2 in, the actual measurements are

From the figure, the analysis indicates that the correct mean is
μ = 3 in = 3*2.54 cm = 7.62 cm
The correct standard deviation is
2.934 in = 2.934*2.54 cm = 7.45 cm
Answer:
μ = 7.62 cm
σ = 7.45 cm