# SOCR EduMaterials AnalysisActivities NormalPower Power Random

### From Socr

### SOCR Normal Power Activity: Look for Power with Generated Data, Background

With two parent distributions, both of the same standard deviation (**sigma**), and we already know the power we want, we'd like to find the sample size needed. The significance level needs to be provided by the user.

The two hypotheses are written as:

**H_0** the true mean, **mu**, is equal to some constant, **mu_0**.

**H_A**: the true mean, **mu**, is not equal to **mu_0**. And we are testing for another possible mean, **mu_A**.

Note that, H_A can be testing the cases of **mu_0 > mu_A**, and **mu_0 < mu_A**. The options are also provided by this tool.

### SOCR Normal Power Activity: Look for Power with Generated Data, Example

You'll first need to tell the computer to generate some data for you. The distribution's paramters (mean and standard deviation) are calucluated from the randomly generated data. The sample size is computed as well. And then, you need to input the mean for the alternative hypothesis for the power of the test.

**1.** Click on **DATA** and then **RANDOM EXAMPLE** to generate random data.

**2.**The result will not be computed until you tell the computer which column of the data you'd like to compute for. So, if you clikc on **CALCULATE**, you'll see an error message like this.

Just click on **MAPPING** and you'll see a screen like below. Here, we only have one column, X. Click on **ADD** to include X for compuation.

**3.** After you do the mapping, the mean and standard deviation of the data are calculated and show in the **SELECT PARAMETER** panel.

But we don't have the mean for the alternative yet, neither have we determined what type of hypothesis testing (less than? greater than? not equal to?) to use. So, if you click **CALCUALTE** without inputting everything in the **SELECT PARAMETERS** panel, you'll see an error message.

**4.** Be sure to select **Get Power Using Sample Size**. Have all the fields filled out, and then click on **CALCULATE** and then **RESULT**, the results are given.

**5.** Click on the **GRAPH** button to see a function of possible values of power.

**6.** Also, click on the **COMPARE CURVES** to see the data, the population, and distribution of mean.

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