Answer:
1) 6 1/2
Step-by-step explanation:
Put 3 1/4 where "a" is and do the arithmetic.
2(3 1/4) = 2·3 + 2·(1/4) = 6 2/4 = 6 1/2
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:
They are 9, 5 and 8
Step-by-step explanation:
It really depends on what month or year. but typically a month is 4-5 weeks so it's either 16 or 20 miles