STAT 35000, Intro to Statistics Homework 11
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STAT 35000, Intro to Statistics
Homework 11
Due date: Wed Apr 5 01:00:00 am 2023 (EDT)
(10 points + 1 point BONUS) One-Way ANOVA: data le: OilPrice_clean.txt
Dierence in log oil price per barrel converted to 2000 USD using the actual ination factor (lOilPrice) in dierent continents (ContName).
We are interested in comparing the log oil price in four continents: "Asia", "Europe", "North America" and "South America". Note that the dataset has six continents: "Asia", "Europe", "North America", "South America", "Oceania" and "Africa". Because of the political unrest in Africa and the unique situation of the countries in Oceania, these continents have diferent prices then the other four continents. There- fore, we are only interested in the irst four continents.
Since the data is provided, it is easier and more accurate to follow the procedures in the tutorials for this computer as- signment. You will lose points if those procedures are not followed.
(1 pt.) 1. Code. Remember to use subset() and remove unused levels of categorical variables. Please see Tutorial 7.2 for details.
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(1.8 pts.) 2. Looking at the data.
(0.9 pts.) 2a. Create a side-by-side boxplot and efects plot of the data and create a table containing the sample size, mean, and standard deviation for each continent. Besides the table, be sure to include all output necessary to create the table. Please upload all of the information below.
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(0.4 pts.) 2b. Please comment on each of the plots and the table.
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(0.5 pts.) 2c. From this information, do you think that the population mean log oil price is diferent for the diferent continents? Please explain your answer.
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(1.5 pts.) 3. Examine the assumptions necessary for ANOVA. Please check them using the appropriate plots/data. Remember, you need to generate the normal probability plots and histograms for each treatment group. It is essential that the histograms are plotted on the same scale as is demon- strated in the tutorial.
(0.2 pts.) 3a. Upload your output here.
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(1.3 pts.) 3b. Is it appropriate to continue the analysis? Be sure to state each of the assumptions and state whether they are valid or not and why. One of the assumptions can be assumed true, but please state it nonetheless.
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(2.5 pts.) 4. Report the results of the ANOVA signiicance test (four steps) using a signiicance level of 0.01.
(0.2 pts.) 4a. Upload your output here.
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(2 pts.) 4b. Please write the four steps below. Be sure to include all of the necessary degrees of freedom.
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(0.3 pts.) 4c. Are your results in this part consistent with what you stated in part 2? Please explain your answer. Note that part 2 is a subjective procedure whereas part 4 is objec- tive.
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(1.7 pts.) 5. Use an appropriate multiple-comparison method to compare the population average log oil price for each continent at a 0.01 signiicance level. Be sure to include the critical value. Present a visual representation of the results.
(0.3 pts.) 5a. Explain why you chose this multiple- comparison method.
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(0.5 pts.) 7a. Code (Please copy it here even if you included it in part 1.)
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(0.2 pts.) 7b. Upload your output here.
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(0.3 pts.) 7c. State which of the treatment levels are diferent from the control and how they are diferent, either above or below the control. Be sure to use complete English sentences. Is this the result the same as for the Tukey analysis? No explanation is required.
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(0.9 pts.) 5b. Upload your output and the graphical repre- sentation here.
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(0.5 pts.) 5c. State the critical value and write a short statement for your conclusion in complete English sentences.
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(1.5 pts.) 6. Write a short paragraph to describe and ex-plain the diference between the population average log oil price for the diferent continents. What are the practical conclusions to the inference performed in the computer as-signment? What is your inal conclusion on the impact of continent on the log oil price? In addition, discuss whether this data can be generalized to other countries not listed.
This paragraph should be written in complete English sen-tences and should be understandable to someone who has not taken a course in Statistics.
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(1 pt. BONUS) 7. Assuming that Asia is the control, perform the Dunnett multiple-comparison test at a 1% sig-niicance level. Hint: This uses another library.
2023-04-05