E-CodeConfidence intervals: z, t, proportion, two-sample — a TI-84 Plus CE program
CONFINT is a TI-BASIC program for the TI-84 Plus CE. Confidence interval for a mean (sigma known or not), a proportion, or a difference of two means (Welch): lower and upper limits, center, margin of error, critical value and degrees of freedom.
What it asks for and what it shows
It asks for 4 values at its prompts, after you pick option 1 from its menu. In the example below it shows LOWER, UPPER, CENTER, MARGIN, CRIT.
Example run
One of its oracle test cases: “z 95%: xbar 102.5 sigma 10 n 36”. The inputs are typed in order, and the results are the values the case expects on the screen.
| Step | Value |
|---|---|
| You enter | |
| Menu | option 1 |
| Input 1 | 0.95 |
| Input 2 | 102.5 |
| Input 3 | 10 |
| Input 4 | 36 |
| The screen shows | |
LOWER= | 99.23339336 |
UPPER= | 105.7666066 |
CENTER= | 102.5 |
MARGIN= | 3.266606641 |
CRIT= | 1.959963985 |
How it's checked
8 test cases, each checked against an independent method. Replayed key by key on a virtual TI-84 Plus CE, they make 52 checks.
How E-Code checks every program
Run it or put it on your calculator
- Open the library in the TI-84 Plus CE calculator and pick “Confidence intervals: z, t, proportion, two-sample” (CONFINT).
- Put it on your own calculator with a computer and a USB cable, or type it in by hand.
Related programs
- Sample size for a margin of error
- Hypothesis tests: z, t, two-sample t, chi-square
- Regression: linear, quadratic, exponential with r²
- Binomial, Poisson and normal probabilities
- One-way ANOVA
All TI-84 Plus CE statistics programs · All TI-84 Plus CE programs