The following questions do not require any Excel calculations. You are asked to
ID: 3357281 • Letter: T
Question
The following questions do not require any Excel calculations. You are asked to interpret the statistical results shown in this table for the “Change in aortic-jet velocity (m/sec/yr)” variable:
In the “Atorvastatin-Placebo adjusted difference” column, what does the value “0.002” represent?
In the “Atorvastatin-Placebo adjusted difference” column, explain how the value “0.002” was calculated.
Interpret the Confidence Interval in the “Atorvastatin-Placebo adjusted difference” column.
Table 2. Progression from Baseline ofAortic-Valve Stenosis on Echocardiography and Computed Tomography. Adjusted Difference: Atorvastatin-Placebo (95% CI) All Patients Placebo P Value Variable Echocardiography No. of patients Change in aortic-jet velocity (m/sec/yr) Increase in peak gradient (mm Hglyr) Change in aortic-valve area (cm 2/yr) Computed tomography No. of patients Absolute change in aortic-valve calcium score Atorvastatin 65 0.201±0.208 0.199±0.210 0.203±0.208 6.48±7.43 -0.081±0. 107-0.079±0. 107-0.083±0.107 134 69 0.002(-0.066 to 0.070) 0.21 (-2.02 to 2.45) 0.007 (-0.026 to 0.040) 0.95 0.85 0.68 6.52±7.24 6.56±7.10 133 64 69 1608+1865 15641956 1648+1790 85 (-554 to 723) 0.80 (AU/yr) Change in log aortic-valve calcium score (per yr) 0.20±0.16 0.20±0.16 0.20±0.15 0.00 (-0.05 to 0.05) 0.93 * Plus-minus values are means ±SD. CI denotes confidence interval, and AU arbitrary units.Explanation / Answer
Question
In the “Atorvastatin-Placebo adjusted difference” column, what does the value “0.002” represent?
Answer:
The value 0.002 in the “Atorvastatin-Placebo adjusted difference” column represent the point estimate for average adjusted difference in the Atorvastatin and Placebo.
Question
In the “Atorvastatin-Placebo adjusted difference” column, explain how the value “0.002” was calculated.
Answer:
We are given a confidence interval as (-0.066, 0.070)
Mean difference – E = -0.066 (equation 1)
Mean difference + E = 0.070 (equation 2)
(E is the margin of error)
Add equation 1 and 2, we get
2*Mean difference + 0 = -0.066 + 0.070
2*Mean difference = 0.004
Mean difference = 0.004/2 = 0.002
(We can also compute it as below:
Point estimate for atorvastatin = 0.199
Point estimate for Placebo = 0.203
Absolute Difference = 0.203 – 0.199 = 0.004
Adjusted difference = 0.004/2 = 0.002
Question
Interpret the Confidence Interval in the “Atorvastatin-Placebo adjusted difference” column.
Answer:
The interpretation of the 95% confidence interval for adjusted difference in the Atorvastatin and Placebo is given as below:
We are 95% confident that the average adjusted difference in the Atorvastatin and Placebo will be lies between -0.066 and 0.070. There is 95% chance that the adjusted difference in the Atorvastatin and Placebo will be included in the confidence interval (-0.066, 0.070).
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