Using the t-distribution to build the 99% confidence interval, it is found that:
- The margin of error is of 3.64.
- The 99% confidence interval for the population mean is (19.36, 26.64).
<h3>What is a t-distribution confidence interval?</h3>
The confidence interval is:

In which:
is the sample mean.
- s is the standard deviation for the sample.
The critical value, using a t-distribution calculator, for a two-tailed 95% confidence interval, with 21 - 1 = 20 df, is t = 2.086.
The other parameters are given as follows:

The margin of error is given by:

Hence the bounds of the interval are:


The 99% confidence interval for the population mean is (19.36, 26.64).
More can be learned about the t-distribution at brainly.com/question/16162795
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Answer: 4,986.875
Step-by-step explanation: Multiply 25.25 x 19.75. Then, multiply the product by 10, or shift the decimal point one place to the right.
The x-coord. of the vertex is halfway between the given zeros. Here, it'd be halfway between x=3 and x=9, which comes out to x = 6 (answer).