Using the t-distribution, it is found that the test statistic for the hypotheses test is given by:

<h3>What are the hypotheses tested?</h3>
At the null hypotheses, it i tested if the mean difference remains the same, that is:

At the alternative hypotheses, it is tested if it has decreased, hence:
.
<h3>What is the test statistic?</h3>
The test statistic is given by:

The parameters are:
is the sample mean.
is the value tested at the null hypothesis.
- s is the standard deviation of the sample.
The parameters are given as follows:
.
Hence the test statistic is given by:


More can be learned about the t-distribution at brainly.com/question/16162795
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9mph because 20 minutes time 3 is one hour so multiply 3 by 3 to get 9
Number of combinations = (6x5) ÷ 2 = 15
Answer:There are 15 combinations
The correct answer would be d (2,-5)
6√5 - 4√7 would be your answer.
<em />I hope this helps love! :)