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The article "'A Study of Wood Stove Particulate Emissions" (J. of the Air Pollution Control Assoc., 1979:\({\rm{724 - 728}}\)) reports the following data on bum time (hours) for samples of oak and pine. Test at level .05 to see whether there is any difference in true average burn time for the two types of wood.

Short Answer

Expert verified

Therefore,

Reject null hypothesis

Step by step solution

01

Step 1:Null hypothesis versus   alternative hypothesis.

When testing null hypothesis

\({H_0}:{\mu _1} - {\mu _2} = {\Delta _0}\)

versus one of the alternative hypothesis, one could use test statistic value

\(w = \sum\limits_{i = 1}^m {{r_i}} \)

Where\(\)\({r_i}\) is rank of\(\left( {{x_i} - {\Delta _0}} \right)\) in the combined sample of\(m + n{\left( {x - {\Delta _0}} \right)^\prime }{\rm{s}}\) and \({y^\prime }s\).

The\(P\)-value depends on alternative hypothesis
Alternative Hypothesis\(P\)-value

\(\begin{array}{l}{H_a}:{\mu _1} - {\mu _2} > {\Delta _0}{P_0}(W \ge w)\\{H_a}:{\mu _1} - {\mu _2} < {\Delta _0}{P_0}(W \le w) = {P_0}(W \ge m(m + n + 1) - w)\\{H_a}:{\mu _1} - {\mu _2} \ne {\Delta _0}2{Y_0}(W \ge \max \{ w,m(m + n + 1) - w)\end{array}\)

Use Table\(A.14\)to determine\({P^2}\)-values (use closest value to corresponding significance level to make conclusions).
The null hypotheses of interest are

\({H_0}:{\mu _1} - {\mu _2} = 0,\)

versus alternative hypothesis

\({H_a}:{\mu _1} - {\mu _2} \ne 0\)

The following table represents required data to compute test statistic value.

02

To draw table for test statistic value.

\(i\)

\({x_i}/{y_i}\)

\({r_i}\)

\(\sum {{r_i}} \)

\(1\)

\(1.72\)

\(13\)

\(2\)

\(0.67\)

\(2\)

\(3\)

\(1.55\)

\(11\)

\(4\)

\(1.56\)

\(12\)

\(5\)

\(1.42\)

\(9\)

\(6\)

\(1.23\)

\(6\)

\(7\)

\(1.77\)

\(14\)

\(m = 8\)

\(0.48\)

\(1\)

\(68\)

\(1\)

\(0.98\)

\(4\)

\(2\)

\(1.4\)

\(8\)

\(3\)

\(1.33\)

\(7\)

\(4\)

\(1.52\)

\(10\)

\(5\)

\(0.73\)

\(3\)

\(n = 6\)

\(1.2\)

\(5\)

\(37\)

03

To determine the each bonding.

The alternative hypothesis is two-sided; thus, the-value is

\(2{P_0}\left( {W \ge \max \{ w,m(m + n + 1) - w) = 2{P_0}(W \ge 37)} \right.\)

Using the table in appendix, for\(\alpha = 0.05\), since\(w = 37 < {W_{m,n,\alpha /2}} = 61\)

the corresponding\(P\)-value is larger than\(0.05\).

Hence, do not reject null hypothesis at given significance level, the mean burning time of two types of wood is the same.

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Most popular questions from this chapter

The ranking procedure described in Exercise 35 is somewhat asymmetric, because the smallest observation receives rank 1, whereas the largest receives rank 2, and so on. Suppose both the smallest and the largest receive rank 1, the second smallest and second largest receive rank 2, and so on, and let W鈥欌 be the sum of the X ranks. The null distribution of W鈥欌 is not identical to the null distribution of W, so different tables are needed. Consider the case m = 3, n = 4. List all 35 possible orderings of the three X values among the seven observations (e.g., 1, 3, 7 or 4, 5, 6), assign ranks in the manner described, compute the value of W鈥欌 for each possibility, and the tabulate the null distribution of W0. What is the P-value if w鈥欌 = 9? This is the Ansari-Bradley test; for additional information, see the book by Hollander and Wolfe in the chapter bibliography.

The sign test is a very simple procedure for testing hypotheses about a population median assuming only that the underlying distribution is continuous. To illustrate, consider the following sample of 20 observations on component lifetime (hr):

1.7 3.3 5.1 6.9 12.6 14.4 16.4

24.6 26.0 26.5 32.1 37.4 40.1 40.5

41.5 72.4 80.1 86.4 87.5 100.2

We wish to test \({H_0}:\tilde \mu = 25.0\) versus \({H_0}:\tilde \mu > 25.0\)The test statistic is Y 5 the number of observations that exceed 25

a. Determine the P-value of the test when Y 5 15. (Hint: Think of a 鈥渟uccess鈥 as a lifetime that exceeds 25.0. Then Y is the number of successes in the sample. What kind of a distribution does Y have when\(\tilde \mu = 25.0\)?)

b. For the given data, should H0 be rejected at significance level .05? (Note: The test statistic is the number of differences \({X_i} - 25\)that have positive signs, hence the name sign test.)

High-pressure sales tactics or door-to-door salespeople can be quite offensive. Many people succumb to such tactics, sign a purchase agreement, and later regret their actions. In the mid-1970s, the Federal Trade Commission implemented regulations clarifying and extending the rights of purchasers to cancel such agreements. The accompanying data is a subset of that given in the article 鈥淓valuating the FTC Cooling-Off Rule鈥 (J. of Consumer Affairs, 1977: 101鈥106). Individual observations are cancellation rates for each of nine sales people during each of 4 years. Use an appropriate test at level .05 to see whether true average cancellation rate depends on the year.

Compute the\(90\% \)rank-sum \(CI\) for\({\mu _1} - {\mu _2}\)using the data in Exercise\(11\).

The article 鈥淧roduction of Gaseous Nitrogen in Human Steady-State Conditions鈥 (J. of Applied Physiology, 1972: 155鈥159) reports the following observations on the amount of nitrogen expired (in liters) under four dietary regimens: (1) fasting, (2) 23% protein, (3) 32% protein, and (4) 67% protein. Use the Kruskal-Wallis test at level .05 to test equality of the corresponding \[{\mu _I}'s\].

1 4.079 4.859 3.540 5.047 3.298

2 4.368 5.668 3.572 5.848 3.802

3 4.169 5.709 4.416 5.666 4.123

4 4.928 5.608 4.940 5.291 4.674

1 4.679 2.870 4.648 3.847

2 4.844 3.578 5.393 4.374

3 5.059 4.403 4.496 4.688

4 5.038 4.905 5.208 4.806

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