Using TI-89 for confidence intervals

In summary, to calculate phi(z) when doing a confidence interval using a TI-89, you can use the Normal CDF function with lower and upper values, or search for specific PDF books on using the TI-89 for probability calculations. The error function, erf(z), is not built in and integrating it is not possible due to its nonstandard nature.
  • #1
jaejoon89
195
0
How do you use a TI-89 to get phi(z) when you do a confidence interval, i.e.

phi(z) = 1/2 (1 + erf(z / sqrt(2)))

The Normal CDF function has lower and upper values so I don't see how I can do it, and erf(z) doesn't do anything when I enter it so it must not be built in. Integrating the error function doesn't work either, I think because it's nonstandard.

ex - using TI 89 to calculate phi(4.5) = .999997
 
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  • #2
Google search Ti-89 and probability. There are usually in pdf format books by Ti on specific topics you can download and/or print.
 

Related to Using TI-89 for confidence intervals

What is a confidence interval and why is it important?

A confidence interval is a range of values that is likely to contain the true value of a population parameter with a certain level of confidence. It is important because it allows scientists to estimate the true population parameter based on a sample and also assess the precision of the estimate.

How do I calculate a confidence interval using a TI-89 calculator?

To calculate a confidence interval using a TI-89 calculator, you will need to use the STAT button and go to the TESTS menu. Then select the appropriate test (t-test, z-test, etc.) for your data and enter the necessary information such as sample size, mean, and standard deviation. The calculator will then display the confidence interval.

What is the significance level and how does it affect the confidence interval?

The significance level, also known as alpha, is the probability of rejecting the null hypothesis when it is actually true. It is typically set at 0.05 or 0.01. The confidence interval will become wider as the significance level decreases, meaning there is a higher level of confidence that the true population parameter falls within the interval.

Can I use a TI-89 calculator to calculate confidence intervals for any type of data?

Yes, a TI-89 calculator can be used to calculate confidence intervals for both numerical and categorical data. However, the appropriate test and formula may vary depending on the type of data being analyzed. It is important to consult a statistics textbook or seek assistance from a statistician when dealing with complex data.

How can I interpret the results of a confidence interval calculated using a TI-89 calculator?

The confidence interval will consist of two values, an upper and lower bound. These values represent the range of values that are likely to contain the true population parameter with a certain level of confidence. A wider interval suggests a less precise estimate, while a narrower interval suggests a more precise estimate. Additionally, if the interval includes the null value (typically 0), then the results are not statistically significant.

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