10.91 Surgery versus placebo for knee pain Refer to Example 10 on whether arthroscopic surgery is better than placebo. The following table shows the pain scores one year after surgery. Using software (such as MINITAB) that can conduct analyses using summary statistics, compare the placebo to the debridement group, using a 95% confidence interval. Use the method that assumes equal population standard deviations.

Explain how to interpret the interval found by using software.

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Group Sample Size Mean Placebo 60 48.9 Knee Pain Score Standard Deviation 21.9 Arthroscopic- 61 54.8 19.8 lavage Arthroscopic 59 51.7 22.4 debridement