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5. Comparing Different Measurement Sets

Two survey crews measure different horizontal angles multiple times; their results are shown in the table. 

  Crew A Crew B
  2 D/R 4 D/R
Average Angle 128°18'15" 196°02'40"
Std Dev ±00°00'12" ±00°00'14"


D/R means to measure an angle direct and reverse; each D/R set is 2 measurements

Which crew has better precision?

Crew A because their standard deviation is smaller.

Which crew has better accuracy?

We need to determine the expected error in each crew’s average angle. Use Equation D-4.

Crew A:   img26a
Crew B:   img27a


 Crew B has better accuracy since the expected error in their average angle is less.

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