Assignment 3 due Thursday Oct. 11

Transcription

1 Instructor Linda C. Stephenson due Thursday Oct. 11 GENERAL NOTE: These assignments often build on each other what you learn in one assignment may be carried over to subsequent assignments. If I have already given detailed instructions for a procedure once, I will not repeat them in following assignments. Part A. Electricity Access for Countries of the World For this part of the assignment, you will be working with data that gives the percent of the population that has access to electricity (measurement unit: %) for 214 countries in the world. One set of data applies to the urban areas of each country, and the second set of data applies to the rural areas of each country. The data is current as of different years for various countries, but generally ranges from 2012 to The source of data is the CIA World Factbook, at the following website: From the website, here is their definition of the data: The data for the assignment is given in the Excel file: electrification_by_country_cia As with Assignment 2, I provided three different sheets of data in the Excel file, and again the tabs for each sheet are located at the bottom of the spreadsheet. The data that you want to copy over to STATDISK is on the STATDISK sheet. Page 1 of 11

2 Instructor Linda C. Stephenson Remember to just copy over the numbers, NOT the column headings. The other two sheets are for your information only, and contain the respective data sorted in order from smallest to largest percentages of electrification, along with the corresponding country names. You will probably want to consult these sorted data lists when you are answering the questions. Column A on the STATDISK sheet contains the country names, column B contains the Urban % Electrification, and column C contains the Rural % Electrification (each in units of %). Copy the data from the STATDISK EXCEL sheet to STATDISK. Start in cell B3, drag down and over to cell C216, and copy that data to STATDISK. So you now have the Urban % in column 1, and the Rural % in column 2. You may want to edit your column titles in STATDISK to reflect this. Make sure that you have a total of 214 rows of data in STATDISK. Use STATDISK to calculate the descriptive statistics for each data set. Hit Data/Explore Data - Descriptive Statistics, select column 1 (Urban %), and hit Evaluate. Print out this ENTIRE output, or snip/screen print it to a file for printing. Repeat for column 2 (Rural %). Print these out and clearly label which is which. Notice that the output includes a histogram of the data. In some cases, it may be better to make your own histogram, to adjust the class width etc., but I felt that these histograms as is were representative of the data, so there is no need to make a separate histogram. Notice that the output also includes a boxplot. IGNORE THESE! The problem is that it is just a regular boxplot, not a modified boxplot. You will make modified boxplots below. You will need to find the mode of the each data set yourself, because STATDISK does not report that. You can refer back to the Excel data file, and look at the data sheets which contain the sorted data. Page 2 of 11

3 Instructor Linda C. Stephenson Next, use STATDISK to make a modified boxplot of the data sets. In this case, I want to you plot BOTH data sets on a single plot. Go to Data/Boxplot, check BOTH columns 1 and 2, and make sure to hit the Modified Boxplot button at the bottom, which will indicate the potential outliers on the graph. For the boxplots, you can use either the Print or Copy button at the bottom. If you hit Copy, then you can just transfer it to a Word file and paste it in (Ctrl-v). You will need to go back and add a title and x-axis label. Clearly indicate which plot is which. That s all the STATDISK calculations you need to do for this portion of the assignment. Also, see below under What you Need to Turn In. Page 3 of 11

4 Instructor Linda C. Stephenson Part B. Would You Like Fries With That? For this part of the assignment, you are going to hit the streets and collect some data. In particular, you are going to take data on how long it takes a customer to receive their food when going through the drive-through window at a fast food restaurant. You may want to work with someone from class on this part of the assignment, so that you can more efficiently collect the data. EVERYONE needs to participate in collecting the data, you cannot just have someone else collect it and provide it to you! Also, note that you still need to both do your own computer work! In addition, although you may discuss your answers with each other, everyone needs to do their own written work for the answers to the questions. I should not receive any assignments that are basically duplicates of each other. You should collect 30 observations. To make sure all of the data is consistent, start timing the interaction when the customer first gets to the ordering screen/microphone. Finish timing the interaction when the customer drives away with all of their food. Watch out for any cases where the customer has to pull into the parking lot and wait for the rest of the order. Collect all of your data in one session that is, don t go in the morning to time 10 interactions and then go back in the evening to get another 20. Pick whichever restaurant and location you want. Try to not get arrested for loitering while you are doing this. SERIOUSLY!!! Enter your 30 data values (times in seconds) into STATDISK. When you first start the program up, there is just a blank grid with no data values. Type your data into column one, with one data value per cell, so you should have a column of 30 data values. Snip and save your data column for printing I cannot grade this portion without your data! Page 4 of 11

5 Instructor Linda C. Stephenson Make a histogram of the data and print it out. Don t just use the histogram from the Descriptive Statistics, I want you to actually use the Histogram option. Remember that you can adjust the number of data classes, etc., by choosing the User Defined option, to get a better looking histogram. So play around with that, and get the best (most representative) histogram that you can. Make sure to add a title and an x-axis label with units. Also make a modified boxplot of the data, print it out, and add a title and an x-axis label. Calculate the descriptive statistics (as described above) for your data, and print out the results. Use these calculations to answer the questions on the Answer Sheet. WHAT YOU NEED TO TURN IN! Part A. Electricity Access for Countries of the World Printout of the descriptive statistics for both data sets from STATDISK. Label them so that I can identify which is which. Printout of the modified boxplot from STATDISK (including BOTH data sets), with a title and x axis label (including units) added. Clearly label which plot is which data set. Part B. Would You Like Fries With That? Printout of your 30 data values (in seconds) that you entered into STATDISK. Printout of your histogram of the time data. Make sure to add a title and x- axis label (including units). Printout of the modified boxplot from STATDISK, with a title and x axis label (including units). Printout of the descriptive statistics from STATDISK. Label this so that I can identify it. For all sections turn in the completed Answer Sheets (6 pages total). Page 5 of 11

6 Part A. Answer Sheet Electricity Access for Countries of the World 1. Based on your histogram/box-plot of both the Urban % and Rural % Electrification data, how would you describe the distribution of the data sets (i.e. the shape)? 2. Why do you think the data (both sets) is distributed like this? Consider the underlying reasons based on the countries, not just the mechanics of the data. 3. Based on the measures of variation that you calculated (question 8), which of the data sets displays more variability? 4. Why do you think that data set (indicated in your answer to question 3) displays more variability? Again, consider the underlying reasons, not just the mechanics of the data. Page 6 of 11

7 5. Pick one of the countries on the list that was on the lower end of % access to electrification (either Urban or Rural). Answer the following, and provide your source below: Country: Why did you pick this country? Investigate WHY (some specific underlying reasons) this country has such a low % access to electrification: List your source: (website link): Page 7 of 11

8 6. List the following measures of center for each data set (all are in % ): % Urban: % Rural: Mean = Mean = Median = Median = Mode = Mode = 7. Which measure of center would you quote for each data set, and why? Page 8 of 11

9 8. List the following measures of variation for each data set (all are in % ): % Urban: % Rural: Range = Range = Std Dev = Std Dev = IQR = IQR = 9. Which measure of variation would you quote for each data set, and why? 10. Use the IQR to calculate the lower and upper fences for each data set (all are in % ). Note: the lower fences may be negative. % Urban: % Rural: Lower fence = Lower fence = Upper fence = Upper fence = 11. Based on these limits, list any data values that are outliers. Note: list the country name, along with its data value in parens (). % Urban: % Rural: Page 9 of 11

10 Part B. Would You Like Fries With That? 1. Provide a description of how you collected your data, including the name (if anyone) of whom you worked with. Also include: the restaurant, the location, what day and from what time to what time you were there, and anything else that may be relevant. 2. Based on your histogram and modified boxplot of the data, how would you describe the distribution of the data (i.e. the shape)? 3. List the following statistics for the data set (all in seconds): Mean = Median = Mode = Standard Deviation = Range = Interquartile Range = 4. Which measure of center would you quote for this data set, and why? Page 10 of 11

11 5. Which measure of variation would you quote for this data set, and why? 6. Use the IQR to calculate the lower and upper fences for the data set: Lower fence = Upper fence = 7. Based on these fences, list any data values (in seconds) that are outliers: 8. What are some possible sources for the variability in the data that you collected? List at least four. Consider the restaurant operations, the ordering process, the customers, etc. Note that this doesn t have to apply just to the time period when you were observing, but could be generalized to any time that the restaurant is open for business. 9. Are the results of this basically what you expected, or was there anything surprising? Do you have any other conclusions to state? Did anything interesting happen while you were loitering in the parking lot? Page 11 of 11