Use to estimate via a confidence interval or perform a hypothesis test for a population mean.
Confidence Interval for the Mean
- From an open JMP® data table, select Analyze > Distribution.
- Select one or more continuous variables from Select Columns, click Y, Columns (continuous variables have blue triangles), and click OK.
The Upper 95% Mean and Lower 95% Mean shows the 95% confidence interval for the population mean.
Note: To change the confidence level, request a one-sided confidence limit or specify sigma, click on the red triangle for the variable, select Confidence Interval, and select the confidence level or click Other.
One Sample t-Test for the Mean
- From the Distributions report window (shown above), click on the red triangle for the variable and select Test Mean.
- Enter the hypothesized value under Specify Hypothesized Mean, and click OK. We will test the following hypothesis:
H0: m = 40 vs. HA: m ≠ 40. JMP will display:
- The t-statistic.
- P-values for the two-tailed and one-tailed tests.
- A graph to aid in interpreting the p-values, showing the hypothesized mean (center of the curve) and the sample mean (red line).
Interpretation of p-values for this example (using a significance level of 0.05):
1. Prob > |t| is less than 0.05 - reject the null hypothesis that the true mean is 40. This is the two-tailed test. Conclude that the true mean is not 40.
2. Prob > t is greater than 0.05 - fail to reject the null hypothesis that the true mean is <= 40. This is a one-tailed test. There no statistical evidence to reject the null hypothesis.
3. Prob < t is less than 0.05 - reject the null hypothesis that the true mean is >= 40. Conclude that the true mean is less than 40. The confidence interval (38.0 , 39.2) provides an estimate of how different the population mean is from 40.
Notes: To explore how the p-value changes as a function of the difference between the hypothesized mean and the sample mean, click on the red triangle next to Test Mean and select PValue animation. Use the Power Animation tool to examine how power changes under different scenarios. This analysis can also be performed using the Hypothesis Test for One Mean and Confidence Intervals for One Mean Calculators under Help > Sample Index > Calculators or Student > Calculators in JMP Student Subscription.
Visit Discovering JMP > Analyze Your Data > Analyze Distributions and Basic Analysis > Distributions in JMP Help to learn more.