The concern of a study by Baynnon et al. (A-4) were nine subjects with chronic a

Question

The concern of a study by Baynnon et al. (A-4) were nine subjects with chronic anterior cruciate ligament (ACL) tears. One of the variables of interest was the laxity of the anteroposterior, where higher values indicate more knee instability. the researchers found that among subjects with ACL-deficency knees, the mean laxity value was 17.4 mm with standard deviation of 4.3mm.

a) what is the estimated standard error of the mean ?

b) construction the 99 percent confidence interval for the mean of the population from which the 9 subjects may be presume to be a random sample

c) what is the precision of the estimate ?

d) what assumptions are necessary for the validity of the confidence interval you constructed?

Explanation / Answer

a) what is the estimated standard error of the mean ?

standard error = s/sqrt(n) = 4.3/sqrt(9) = 4.3/3 = 1.43333

b) construction the 99 percent confidence interval for the mean of the population from which the 9 subjects may be presume to be a random sample

t-distribution with n-1 = 8 degree of freedom

t0.005 = 3.555

(17.4-3.555* 1.43333),(17.4 + 3.555* 1.43333),

= (12.30451,22.49548)

c) what is the precision of the estimate ?

precision of estimate = 3.555* 1.43333 = 5.095488

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