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You can use the formula ...
... (percent change) = ((new amount) - (original amount))/(original amount) × 100%
Filling in the given information, this tells you ...
... (percent change) = ($21 -$28)/($28) × 100%
... = (-7/28) × 100%
... (percent change) = -25%
A negative percent change is a decrease, so the change in price is a ...
... 25% decrease
They are the same just the fraction and decimal are not the same but your answer is the same or =
Using the t-distribution, it is found that the confidence interval is (14.2, 14.8).
<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 <em>two-tailed 95% confidence interval</em>, with 18 - 1 = <em>17 df</em>, is t = 2.1098.
The other parameters are given by:
.
Hence, the bounds of the interval are given by:


The confidence interval is (14.2, 14.8).
More can be learned about the t-distribution at brainly.com/question/16162795
Exact form: 9/20 and decimal form: 0.45