Ultrasound is often used in the treatment of soft tissue injuries. In an experim

Question

Ultrasound is often used in the treatment of soft tissue injuries. In an experiment toinvestigate the eect of an ultrasound and stretch therapy on knee extension, range of motionwas measured both before and after treatment for a sample of physical therapy patients. Thefollowing data is a subset of data that appears in Trae Tashiros 2003 Ph.D. thesis from theUniversity of Virginia:

Construct a 95% condence interval for the mean change in range of motion (pre-treatment -post-treatment) and interpret this interval. What assumptions were necessary to construct thisinterval?

Explanation / Answer

Group pre-treatment post-treatment
Mean 44.43 47.86
SD 10.00 10.88
SEM 3.78 4.11
N 7 7

The mean of pre-treatment minus post-treatment equals -3.43
standard error of difference = 1.325

df = 6 , t(0.025, df=n-1=6)=2.45 (check student t table)

So 95% CI is

-3.43 ± t*1.325

--> -3.43 ± 2.45*1.325

--> -6.67 to -0.18

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What assumptions were necessary to construct thisinterval?

Normal distribution

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