## Confidence Intervals for a Mean

Your browser doesn't support the ``` canvas ``` element.
 Your browser doesn't support the ``` canvas ``` element. Sample mean: Sample sd: Sample #:
Show population mean:

20 50 100 250
90 95 99
Your browser doesn't support the ``` canvas ``` element.

### Instructions

Applet Overview: The large ‘jar’ contains 10,000 balls of various sizes, from 6 to 60 pixels in diameter. What is the mean diameter length of the balls in the jar?

Measuring the diameters of all balls in the jar could lead us to the true mean, however, a large population like this one is often inaccessible due to constraints of time and other resources. Instead, choose a (much smaller) sample from the population, compute the mean diameter of balls in the sample, and use that to estimate the mean diameter of balls in the whole population.

Buttons:

• Sample – Use this button to choose a single sample from the large jar. The sample will appear in the small jar and the mean diameter of balls in the sample is indicated below the plot. Repeat this process to draw more samples.
• Sample 100 – This button will cause the applet to choose 100 random samples from the large jar in rapid succession. The 100th sample will be shown in the sample jar. Confidence intervals based on the 100 samples are drawn in the plot below.
• Clear plot – This button erases the graph and empties the sample jar but does not change the population. Use this button when you want to look at confidence intervals with a new sample size.
• New Population – This button clears the plot, empties the sample jar, and fills the large jar with a new population of balls.

Other components:

• Show p check box – Use this box to show the value of the parameter, that is, the true proportion of blue balls in the population (large jar). The proportion is displayed beside the check box and is indicated in the plot.
• Sample size radio buttons – Use the radio buttons to set the size of the sample: 50, 100 (default), or 250 balls.
• Confidence radio buttons – The radio buttons can be used to set the confidence level to 90, 95 (default), or 99.