Question

'' Hallux abducto valgus (call it HAV) is a deformation of the big toe that often requires surgery. Doctors used X-rays to measure the angle (in degrees) of deformity in 38 consecutive patients under the age of 21 who came to a medical center for surgery to correct HAV. The angle is a measure of the seriousness of the deformity. Here are the data.

27 21 16

34 17 30

26 14 31

36 21 20

38 25 51

28 15 23

25 32 28

16 27 30

29 19 31

25 21 38

30 21 33

15 19 23

20 26

It is reasonable to regard these patients as a random sample of young patients who require HAV surgery. The data follow a Normal distribution quite closely except for one patient with HAV angle 51 degrees, a high outlier. A good way to judge the effect of an outlier is to do your analysis twice, once with the outlier and a second time without it.

(a) Find the 95% confidence interval for the population mean based on the 37 patients who remain after you drop the outlier. (Round your answers to two decimal places.)

answer: _____ to ______

Answer 1

The statistical software output for this problem is:

Hence,

a) 95% confidence interval will be:

22.92 to 27.35