In this problem, assume that the distribution of differences is approximately normal. Note: For degrees of freedom d.f. not in the Student's t table, use the closest d.f. that is smaller. In some situations, this choice of d.f. may increase the P-value by a small amount and therefore produce a slightly more "conservative" answer. In the following data pairs, A represents the cost of living index for utilities and B represents the cost of living index for transportation. The data are paired by metropolitan areas in the United States. A random sample of 46 metropolitan areas gave the following information. A: 90 82 84 107 85 102 89 123 104 B: 100 92 104 101 111 108 93 115 113 A: 118 133 104 84 80 77 90 92 90 B: 106 95 110 112 105 93 119 99 109 A: 106 95 110 112 105 93 119 99 109 B: 96 109 103 107 103 102 101 86 94 A: 109 113 90 121 120 85 91 91 97 B: 88 100 104 119 116 104 121 108 86 A: 95 115 99 86 88 106 80 108 90 87 B: 100 83 88 103 94 125 115 100 96 127 Do the data indicate that the U.S. population mean cost of living index for utilities is less than that for transportation in these areas? Use ? = 0.05. (Let d = A − B.) (a) What is the level of significance? .05 (b) State the null and alternate hypotheses. Will you use a left-tailed, right-tailed, or two-tailed test? H0: ?d = 0; H1: ?d < 0; left-tailed (c) What sampling distribution will you use? What assumptions are you making? The Student's t. We assume that d has an approximately normal distribution. (d) What is the value of the sample test statistic? (Round your answer to three decimal places.) ????????? (e) Find (or estimate) the P-value. P-value > 0.2500.125 < P-value < 0.250 0.050 < P-value < 0.1250.025 < P-value < 0.0500.005 < P-value < 0.025P-value < 0.005 (f) Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically significant at level ?? (A)At the ? = 0.05 level, we reject the null hypothesis and conclude the data are statistically significant. (B)At the ? = 0.05 level, we fail to reject the null hypothesis and conclude the data are not statistically significant. (C)At the ? = 0.05 level, we reject the null hypothesis and conclude the data are not statistically significant. (D) At the ? = 0.05 level, we fail to reject the null hypothesis and conclude the data are statistically significant.
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
In this problem, assume that the distribution of differences is approximately normal. Note: For degrees of freedom d.f. not in the Student's t table, use the closest d.f. that is smaller. In some situations, this choice of d.f. may increase the P-value by a small amount and therefore produce a slightly more "conservative" answer.
In the following data pairs, A represents the cost of living index for utilities and B represents the cost of living index for transportation. The data are paired by metropolitan areas in the United States. A random sample of 46 metropolitan areas gave the following information.
A: | 90 | 82 | 84 | 107 | 85 | 102 | 89 | 123 | 104 |
B: | 100 | 92 | 104 | 101 | 111 | 108 | 93 | 115 | 113 |
A: | 118 | 133 | 104 | 84 | 80 | 77 | 90 | 92 | 90 |
B: | 106 | 95 | 110 | 112 | 105 | 93 | 119 | 99 | 109 |
A: | 106 | 95 | 110 | 112 | 105 | 93 | 119 | 99 | 109 |
B: | 96 | 109 | 103 | 107 | 103 | 102 | 101 | 86 | 94 |
A: | 109 | 113 | 90 | 121 | 120 | 85 | 91 | 91 | 97 |
B: | 88 | 100 | 104 | 119 | 116 | 104 | 121 | 108 | 86 |
A: | 95 | 115 | 99 | 86 | 88 | 106 | 80 | 108 | 90 | 87 |
B: | 100 | 83 | 88 | 103 | 94 | 125 | 115 | 100 | 96 | 127 |
Do the data indicate that the U.S. population mean cost of living index for utilities is less than that for transportation in these areas? Use ? = 0.05. (Let d = A − B.)
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