A research team is interested in the effectiveness of hypnosis in reducing pain.

Question

A research team is interested in the effectiveness of hypnosis in reducing pain. The responses from 8 randomly selected patients before and after hypnosis are recorded in the table below (higher values indicate more pain). Construct a 90% confidence interval for the true mean difference in pain after hypnosis. Perceived pain levels 'Pre and Post' hypnosis for 8 subjects 10.2 11.4 14.4 9.8 10.7 13.5 Pre 8.3 Post 12.5 12.0 9.2 13.6 11.0 4.2 0.6 4.6 1.9 1.2 2.8 Difference a) Fill in the missing table cells for the pain level differences. Compute the differences as Pre Post b) If the hypnosis treatment is effective in reducing pain, we expect the differences (pre post) to be positive Note: For (c), (d), and (e) use 3 decimals in your answers. You should use JMP to calculate these values c) The point estimate for the true average effect that hypnosis has on pain perception (i.exa is: 051 d) The point estimate for the true standard deviation of the effect that hypnosis has on pain perception (i.e s: 277 e) The standard error for the mean difference in pain scores is: 0982 For this problem the sample size is small enough that approximating the critical value as being t-2 wil induce substantial error. It turns out that, for a sample size of n -8, the 95% t-critical value is about t 2.4. Using this, this 95% confidence interval for the true mean difference in pain level after hypnosis is: IMPORTANT; don't enter the 95% CDMp gives you. It will be wrong, because t critical m 2 4 has been rounded to the nearest deci ns, while a s, uses , mere preciso ralue You need to calculate this yourself using the Ct formula (round your answer to 2 decimals)

Explanation / Answer

(x1 - x2) = -0.513 , SE = 0.982
t value at 95% CI = 2.4

CI = ( x1 - x2) +/- t* SE
= -0.513 +/- 2.4 * 0.982
= -2.8698 , 1.8438
-2.87 < Mud < 1.84

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