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Question
Two forecasting models were used to predict the future values of a time series. The forecasts are shown below with the actual values.
Which model is the most accurate? Why?
Answer
This answer is hidden. It contains 94 characters.
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A study was conducted to investigate the effect of coaching on IQ tests. Nine randomly selected students were tested.Before After100 106111 11293 9592 9099 10785 100117 126110 10598 110Calculate T- and T+.A. 44, 1B. 38.5, 6.5C. 45.5, 2.5D. 32.5, 12.5
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In a Wilcoxon rank sum test, when two or more observations are equal, we assign to each tied observation a rank equal to the _________ of the consecutive ranks.
A. average
B. median
C. sum
D. difference
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The __________________ is a nonparametric counterpart of a small-sample t test for comparing two independent population locations.
A. Wilcoxon rank sum test
B. Kruskal-Wallis H test
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A. reject H0 if rs > .457.
B. reject H0 if rs > .623.
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A cholesterol test was given to 10 heart patients with high cholesterol levels. The same 10 heart patients are then given a new cholesterol-reducing drug for six months. Before the patients begin taking the drug, they are told to maintain their current diets and eating habits so that the effect of the drug can be more effectively determined. After taking the drug for six months, the same patients are given a cholesterol test again. The pharmaceutical company manufacturing the medicine wants to know if the drug is effective in reducing the cholesterol levels of the patients. The cholesterol levels before and after taking the drug are recorded for each patient. The population of cholesterol levels is not normally distributed. Which one of the following nonparametric tests is appropriate for this problem?
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A. Wilcoxon signed ranks test
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The Wilcoxon signed ranks test is the nonparametric counterpart of the
A. large sample test about a single population mean.
B. two independent samples t test.
C. one-way ANOVA F test.
D. paired difference t test.
E. F test for equality of population variances.
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An assumption of the Wilcoxon rank sum test is that the variances of the two populations are equal.
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Nonparametric tests can be more powerful than the corresponding t or F tests if the population distribution is highly skewed or nonnormal.
Q:
In 25 samples of 100 units each, 75 units were found to be defective. Find the appropriate UCL and LCL for the p chart.
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C. 0 to .0812
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Q:
How well a process is able to meet the requirements set forth by the process design is called
A. process leeway.
B. quality of conformance.
C. quality of performance.
D. quality of design.
Q:
If the process variability steadily increases, we would observe
A. an alternating pattern of a high value followed by a low value on the R chart.
B. an upward trend on the R chart.
C. a downward trend on the R chart.
D. an increasing gradual funnel pattern on the R chart.
E. a decreasing gradual funnel pattern on the R chart.
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If a company is using an chart for a given process with measurement data, it is generally not important or necessary to use an R chart or s chart.
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If a process is stable and in statistical control, it is not influenced by assignable causes of variation.
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Control charts are used to reduce common causes of variation.
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A sequence of steadily decreasing points on a control chart is called run down.
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How well the design of the product meets and exceeds the needs and expectations of the customers is called the quality of performance.
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Process leeway is the distance between natural tolerance limits and control limits.
Q:
An chart is a control chart on which individual process measurements are plotted versus time.
Q:
A manufacturer of windows produces one type that has a plastic coating. The specification limits for the plastic coating are 30 and 70. From time to time the plastic coating can become uneven. Therefore, in order to keep the coating as even as possible, thickness measurements are periodically taken at four different locations on the window. 15 subgroups were observed, each consisting of four thickness measurements, with the following results: mean of the means = = 50.05, and average range = 8.85. Calculate the center line for the R chart.
A. 50.05
B. 8.85
C. 2.21
D. 0.59
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A motorcycle manufacturer produces the parts for its vehicles in different locations and transports them to its plant for assembly. To keep the assembly operations running efficiently, it is vital that all parts be within specification limits. One important part used in the assembly is the engine camshaft, and one important quality characteristic is the case hardness depth. Specifications state that the hardness depth must be between 3.0 mm and 6.0 mm. To investigate the process, the quality control engineer selected 25 daily subgroups of n = 5 and measured the hardness depth. The process yielded a mean of the means = 4.50 and an average range = 1.01. Calculate the center line for the X-bar chart.
A. 1.01
B. 4.50
C. 3.49
D. 0.90