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A sample of n sludge specimens is selected and the pH of each one is determined. The one-sample t test will then be used to see if there is compelling evidence for concluding that true average pH is less than 7.0. What conclusion is appropriate in each of the following situations?

a.n= 6, t= -2.3, 伪= .05

b.n= 15, t= -3.1伪=.01

c.n= 12, t= -1.3, 伪= .05

d.n= 6, t = .7, 伪 = .05

e.n= 6, \(\overline x = 6.68,s/\sqrt n = .0820\)

Short Answer

Expert verified

a) Reject the null hypothesis\({H_0}\).

b) Reject the null hypothesis\({H_0}\).

c) Fail to Reject the null hypothesis\({H_0}\).

d) Fail to Reject the null hypothesis\({H_0}\).

e) Reject the null hypothesis \({H_0}\).

Step by step solution

01

Step 1:Null hypothesis.

The null hypothesis, denoted by H0, is the claim that is initially assumed to be true (the 鈥減rior belief鈥 claim). The alternative hypothesis, denoted by Ha, is the assertion that is contradictory to H0.

The null hypothesis will be rejected in favour of the alternative hypothesis only if sample evidence suggests that H0 is false. If the sample does not strongly contradict H0, we will continue to believe in the plausibility of the null hypothesis. The two possible conclusions from a hypothesis-testing analysis are then reject H0 or fail to reject H0.

02

Solution for part a).

Given that,

\(\begin{array}{l}n = 6\\t = - 2.3\\\alpha = 0.05\end{array}\)

Given claim: average is less than \(7.0\)

The claim i either the null hypothesis or the alternative hypothesis. The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis state the opposite of the null hypothesis.

\({H_0}:\mu = 7.0\)

\({H_a}:\mu < 7.0\)

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the students T table in the appendix containing the t-value in the row

\(\begin{array}{l}df = n - 1\\df = 6 - 1\\df = 5\end{array}\)

You need to double the boundaries, because the test is two sided.

\(0.025 < P < 0.05\)

If the P-value is smaller than the significance level, then the null hypothesis is rejected.

\(P < 0.05\), so it is reject \({H_0}\)

03

Solution for part b).

Given that,

\(\begin{array}{l}n = 15\\t = - 3.1\\\alpha = 0.01\end{array}\)

Given claim: average is less than \(7.0\)

The claim i either the null hypothesis or the alternative hypothesis. The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis state the opposite of the null hypothesis.

\({H_0}:\mu = 7.0\)

\({H_a}:\mu < 7.0\)

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the students T table in the appendix containing the t-value in the row

\(\begin{array}{l}df = n - 1\\df = 15 - 1\\df = 14\end{array}\)

You need to double the boundaries, because the test is two sided.

\(0.001 < P < 0.005\)

If the P-value is smaller than the significance level, then the null hypothesis is rejected.

\(P < 0.01\), so it is reject \({H_0}\)

04

Solution for part c).

Given that,

\(\begin{array}{l}n = 12\\t = - 1.3\\\alpha = 0.05\end{array}\)

Given claim: average is less than \(7.0\)

The claim i either the null hypothesis or the alternative hypothesis. The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis state the opposite of the null hypothesis.

\({H_0}:\mu = 7.0\)

\({H_a}:\mu < 7.0\)

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the students T table in the appendix containing the t-value in the row

\(\begin{array}{l}df = n - 1\\df = 12 - 1\\df = 11\end{array}\)

You need to double the boundaries, because the test is two sided.

\(P > 0.10\)

If the P-value is smaller than the significance level, then the null hypothesis is rejected.

\(P > 0.05\), so it is fail to reject \({H_0}\).

05

Solution for part d).

Given that,

\(\begin{array}{l}n = 6\\t = 0.7\\\alpha = 0.05\end{array}\)

Given claim: average is less than \(7.0\)

The claim i either the null hypothesis or the alternative hypothesis. The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis state the opposite of the null hypothesis.

\({H_0}:\mu = 7.0\)

\({H_a}:\mu < 7.0\)

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the students T table in the appendix containing the t-value in the row

\(\begin{array}{l}df = n - 1\\df = 6 - 1\\df = 5\end{array}\)

You need to double the boundaries, because the test is two sided.

\(P > 0.10\)

If the P-value is smaller than the significance level, then the null hypothesis is rejected.

\(P > 0.05\), so it is fail to reject \({H_0}\)

06

Solution for part e).

Given that,

\(\begin{array}{l}n = 15\\\overline x = 6.68\\s/\sqrt n = 0.0820\end{array}\)

Let us assume \(\alpha = 0.05\)

Given claim: average is less than \(7.0\)

The claim i either the null hypothesis or the alternative hypothesis. The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis state the opposite of the null hypothesis.

\({H_0}:\mu = 7.0\)

\({H_a}:\mu < 7.0\)

Determine the vale of the test statistic:

\(\begin{array}{l}t = \frac{{\overline x - {\mu _0}}}{{s/\sqrt n }}\\t = \frac{{6.68 - 7.0}}{{0.0820}}\\t = - 3.90\end{array}\)

07

Solution for part e).

The P-value is the probability of obtaining the value of the test statistic, or a value more extreme. The P-value is the number (or interval) in the column title of the students T table in the appendix containing the t-value in the row

\(\begin{array}{l}df = n - 1\\df = 6 - 1\\df = 5\end{array}\)

You need to double the boundaries, because the test is two sided.

\(0.005 < P < 0.001\)

If the P-value is smaller than the significance level, then the null hypothesis is rejected.

\(P < 0.05\), so it is reject \({H_0}\)

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