In this initial example, you would like to design an experiment that has 90% power to detect a difference of 1.5 seconds at a significance level of α = 0.05. Use the One Sample Mean calculator to calculate the number of samples you need to test.
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Select DOE > Design Diagnostics > Sample Size and Power.
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Click the One Sample Mean button.
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Leave Alpha set to 0.05.
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4.
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Enter 2 for Std Dev.
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Leave Extra Parameters set to 0.
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Enter 1.5 for Difference to detect.
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Leave Sample Size blank.
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Enter 0.9 for Power.
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9.
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Click Continue.
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Figure 17.4 One-Sample Mean Calculator
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Select DOE > Design Diagnostics > Sample Size and Power.
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Click One Sample Mean.
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Leave Alpha set to 0.05.
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4.
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Enter 2 for Std Dev.
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Leave Extra Parameters set to 0.
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Enter 1.5 for the Difference to detect.
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Leave Sample Size blank.
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Leave Power blank.
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Click Continue to launch the power by sample size plot.
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Figure 17.5 Power by Sample Size
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Select DOE > Design Diagnostics > Sample Size and Power.
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2.
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Click One Sample Mean.
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3.
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Leave Alpha set to 0.05.
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4.
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Enter 2 for Std Dev.
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5.
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Leave Extra Parameters set to 0.
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Leave Difference to detect blank.
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Enter 21 for Sample Size.
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Leave Power blank.
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9.
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Click Continue.
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1.
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Select DOE > Design Diagnostics > Sample Size and Power.
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2.
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Click One Sample Mean.
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3.
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Leave Alpha set to 0.05.
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4.
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Enter 2 for Std Dev.
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5.
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Leave Extra Parameters set to 0.
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6.
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Enter 1.5 as Difference to detect.
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7.
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Leave Sample Size blank.
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8.
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Leave Power blank.
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9.
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Click Animation Script.
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Figure 17.7 Initial Animation Script to Illustrate Power
The initial animation plot shows two t-density curves:
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The red curve shows the t-distribution when the true mean is zero.
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The blue curve shows the t-distribution when the true mean is 1.5, which is the difference to be detected.
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By default, the animation shows a two sided test. Use the Two Sided, Low Side, and High Side buttons to toggle between not equal, less than, or greater than alternative hypotheses.