Table 4 Comparison of ideal and real positions with a 95 % confidence interval (unit: mm)

Point 1 (355, −275,50)

26.234 ± 0.021

15.849 ± 0.049

18.793 ± 0.034

22.375 ± 0.023

Point 2 (355, −135,50)

26.522 ± 0.039

17.444 ± 0.065

15.677 ± 0.140

20.094 ± 0.069

Point 3 (495, −275,50)

28.178 ± 0.032

17.122 ± 0.027

26.898 ± 0.038

27.686 ± 0.028

Point 4 (355, −415,50)

27.651 ± 0.075

16.329 ± 0.030

21.531 ± 0.029

23.417 ± 0.028

Point 5 (215, −275,50)

25.949 ± 0.030

16.230 ± 0.132

12.514 ± 0.025

16.230 ± 0.070

Point 6 (355, −275,150)

26.568 ± 0.038

15.643 ± 0.063

19.179 ± 0.049

23.440 ± 0.024

Average error

26.850

16.436

19.099

22.207

Improvement

38.789 %

28.868 %

17.292 %