APPENDIX B EXCEL BASICS 1 Microsoft Excel is a powerful application for education researchers and students studying educational statistics. Excel worksheets can hold data for a variety of uses and therefore serve as a database. We will focus primarily on its use as a spreadsheet, however. This book discusses how students of statistics can use Excel menus to create specific data management and statistical analysis functions. I will use Microsoft Office Excel 2013 for all examples and illustrations in this book. 2 Like other software, Excel changes occasionally to improve performance and adapt to new standards. As I write, other versions are projected; however, most all of my examples use the common features of the application that are not likely to undergo radical changes in the near future. I cannot hope to acquaint the reader with all the features of Excel in this book. My focus is therefore confined to the statistical analysis and related functions called into play when using the data analysis features. I will introduce some of the general features in this appendix and cover the statistical applications in more depth in the procedure chapters. DATA MANAGEMENT The opening spreadsheet presents the reader with a range of menu choices for entering and managing data. Like other spreadsheets, Excel consists of rows and columns for 1 Some material in this appendix is adapted from Abbott (2011), Understanding Educational Statistics Using Microsoft Excel and SPSS. 2 Used with permission from Microsoft. Using Statistics in the Social and Health Sciences with SPSS and Excel, First Edition. Martin Lee Abbott. 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
532 EXCEL BASICS Figure B.1 The initial Excel spreadsheet. entering and storing data of various kinds. Typically, rows represent cases in statistical analyses, and columns represent variables. According to the Microsoft Office website, the spreadsheet can contain over 1,000,000 rows and over 16,000 columns. We will not approach either of these limits; however, you should be aware of the capacity in the event you are downloading a large database from which you wish to select a portion of data. One practical feature to remember is that researchers typically use the first row of data to record variable names in each of the columns of data. Therefore, the total data set contains (rows 1) cases, which takes this into account. Figure B.1 shows the spreadsheet with its menus and navigation bars. I will cover much of the available spreadsheet capacity over the course of discussing our statistical topics throughout the book. Here are some basic features. Data Sheets Figure B.1 shows a Sheet tab on the bottom of the spreadsheet. This is a tab naming this spreadsheet. You may add sheets to this Excel file by selecting the plus button and work on them individually or linked. Many separate worksheets can be contained in the overall workbook file. Although the sheets can be used independently to store data, the statistical user typically places a data set on one sheet and then uses additional sheets for related analyses. For example, as we will discuss in later chapters, each statistical procedure will generate a separate output sheet. Thus, the original sheet of data will not be modified or changed (unless it is specifically linked). The
THE EXCEL MENUS 533 user can locate the separate statistical findings in separate sheets. Each Sheet tab can be named by right-clicking on the sheet. THE EXCEL MENUS The main Excel menus are located in a ribbon at the top of the spreadsheet beginning with FILE and extending several choices to the right. I will comment on these briefly before we look more comprehensively at the statistical features. Home The Home menu includes many options for formatting and structuring the entered data, including a font group, alignment group, cells group (for such features as insert/delete options), and other such features. One set of submenus is particularly useful for the statistical user. These are listed in the Number category located in the ribbon at the bottom of the main set of menus. The default format of Number is typically General shown in the highlighted box (see Figure B.1). If you select this drop-down menu, you will be presented with a series of possible formats for your data among which is the choice Number the second choice in the submenu. If you click this option, Excel returns the data in the cell as a number with two decimal points. When you select the Number button at the bottom of the category box, you can select from several choices that allow you to refine the nature of the data entered, as shown in Figure B.2. (The additional choices for data formats are located in the Category: box located on the left side of this submenu.) We will primarily use this Number format since we are analyzing numerical data, but we may have occasion to use additional formats. You can use this submenu to create any number of decimal places by using the Decimal places: box. You can also specify different ways of handling negative numbers by selecting among the choices in the Negative numbers: box. Insert Tab I will return to this menu many times over the course of our discussion. Primarily, we will use this menu to create the visual descriptions of our analyses (graphs and charts). Page Layout This menu is helpful for formatting functions and creating the desired look and feel of the spreadsheet. Formulas The Formulas menu is a very important part of the statistical arsenal of Excel. We will discuss specific functions as we get to them in the course of our study; for
534 EXCEL BASICS Figure B.2 The variety of cell formats available in the Number submenu. now, I will point out that the first section of this menu is the Function Library that contains a great many categories of functions (i.e., Financial, Logical, Text, etc.). Selecting any of these results in a submenu of choices for formulas specific to that category of use. There are at least two ways to create statistical formulas, which we will discuss in this book: 1. More Functions tabthis tab presents the user with additional categories of formulas, one of which is Statistical. As you can see when you select this tab, there are a great many choices for handling data. Essentially, these are embedded formulas for creating specific statistical output. For example, AVERAGE is one of the first formulas listed when you choose More Functions and then select Statistical. This formula returns the mean value of a set of selected data from the spreadsheet. 2. Insert Functions taba second way to access statistical (and other) functions from the Function Library is using the Insert Function submenu that, when selected, presents the user with the screen shown in Figure B.3. As you can see, I chose AVERAGE which appears in the highlighted bar. Choosing this feature is the way to import the function to the spreadsheet. As you can see, there are a variety of ways to choose a desired function. The Search
THE EXCEL MENUS 535 Figure B.3 The Insert Function submenu of the Function Library. for a function: box allows the user to describe what they want to do with their data. When selected, the program will present several choices in the Select a function: box immediately below it, depending on which function you queried. The Or select a category: box lists the range of function categories available. The statistical category of functions will be shown if double-clicked (as shown in Figure B.3). Accessing the list of statistical functions through this button will result in the same list of functions obtainable through the More Functions tab. When you use the categories repeatedly, as we will use the Statistical category repeatedly, Excel will show the functions last used in the Select a function: box. Data This is the main menu for discussion in this book. Through the submenu choices, the statistical student can access the data analysis procedures, sort and filter data in the spreadsheet, and provide a number of data management functions important for statistical analysis. Figure B.4 shows the submenus of the Data menu (highlighted). The following are some of the more important submenus that I will explain in detail in subsequent chapters. Sort and Filter The Sort submenu allows the user to rearrange the data in the spreadsheet according to a specific interest or statistical procedure. For example, if you had a spreadsheet with two variables, General Health and Sex, you could use the Sort key to arrange the values of the variables according to Sex. (You might
536 EXCEL BASICS Figure B.4 The submenus of the Data menu. recognize these data from the example in Appendix A, Table A.1.) 3 Doing this would result in Excel arranging the Sex categories, 1 (male) and 2 (female) in ascending or descending order (alphabetically depending on whether you proceed from smallest to largest or from largest to smallest ) with the values of the other variable(s) linked to this new arrangement. Thus, a visual scan of the data would allow you to see how the cases of the variables change as you proceed from Sex category 1 to category 2 (male and female) respondents. The following two figures show the results of this example. Figure B.5 shows the first fourteen cases (the category name occupies the top cell, so the 15th line in the spreadsheet is case #14) on the unsorted variables. As you can see from Figure B.5, you cannot easily discern a pattern to the data depending on whether males or females have higher or lower values on GENHLTH scores in this sample. 4 Sorting the data according to the Sex variable may help to indicate relationships or patterns in the data that are not immediately apparent. Figure B.6 shows the same variables sorted according to SEX (sorted smallest to largest resulting in the male scores listed first). 3 Centers for Disease Control and Prevention (CDC). Behavioral Risk Factor Surveillance System Survey Data. Atlanta, Georgia: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2013. 4 The example data represent a very small number of cases, so there is no attempt to make research conclusions about the variables shown.
THE EXCEL MENUS 537 Figure B.5 Unsorted data for the two-variable database. Figure B.6 shows the data arranged according to the categories of the Sex variable. Viewed in this way, you can detect some general patterns. It appears, generally, that female students indicated generally higher scores on GENHLTH than males. Of course, this small sample is not a good indicator of the overall relationship between Sex and general health. An important operational note for sorting is to first select the entire database before you sort any of the data fields (by clicking on the box above the numbered cases and to the left of the lettered variables). If you do not sort the entire database, you can inadvertently only sort one variable, which may result in the values of this variable disengaging from its associated values on adjacent variables. In these cases, the values for each case may become mixed. Selecting the entire database before any sort ensures that the values of a given variable remain fixed to the values of all the variables for each of the cases. The Filter submenu is useful in this regard. Excel adds drop-down menus next to each variable when the user selects this submenu. When you use the menus, you can specify a series of ways to sort the variables in the database without disengaging the values on the variables. You can also perform a multiple sort in Excel using the Sort menu. Figure B.7 shows the submenu presented when you choose Sort. As you can see from the screen, choosing the Add Level button in the upper left corner of the screen results in a second sort line ( Then by ) allowing you to specify a second sort variable. This would result in a sort of the data first by SEX, and then the values of GENHLTH would be presented low to high within both categories of SEX. Excel also records the nature of the variables. Under the Order column on the far right of Figure B.7, the variables chosen for sorting are listed as Smallest to
538 EXCEL BASICS Figure B.6 Using the Sort function to arrange values of the variables. Figure B.7 The Excel submenu showing a sort by multiple variables. Largest, indicating they are numeric or represent numbers rather than letters. Text variables are composed of values (either letters or numbers) that are treated as letters and not used in calculations. If the SEX values in Figure B.6 had been listed as Male and Female and not coded as 1 or 2 in the original data set, Excel might treat the values differently in calculations (since letters cannot be added, subtracted, etc.). In this case I would want to ensure that the 1 and the 2 would be treated as a number. Be sure to format the cells properly (from the Number group in the Home menu) so that you can be sure the values are treated as you intend them to be treated in your analyses.
THE EXCEL MENUS 539 Figure B.8 The Excel screen showing the results of a multiple sort. Figure B.9 The Data Analysis submenu containing statistical analysis procedures. Figure B.8 shows the resulting sort. Here you can see that the data were first sorted by SEX, and then the values of GENHLTH were presented low to high in value within both SEX categories. Data Analysis This submenu choice (located in the Data tab in the Analysis group) is the primary statistical analysis device we will use in this book. Figure B.4 shows the Data Analysis submenu in the upper right corner of the menu bar. Choosing this option results in the box shown in Figure B.9.
540 EXCEL BASICS Figure B.10 The Add-In options for Excel. Figure B.9 shows the statistical procedures available in Excel. The scroll bar to the right of the screen allows the user to access several additional procedures. We will explore many of these procedures in later chapters. You may not see the Data Analysis submenu displayed when you choose the Data menu on the main Excel screen. That is because it is often an add-in program. Not everyone uses these features so Excel makes them available as an adjunct. 5 If your Excel screen does not show the Data Analysis submenu in the right edge of the menu bar when you select the Data menu, you can add it to the menu. Select the Office Button in the upper left corner of the screen, and then you will see an Excel Options button in the lower center of the screen. Choose this and you will be presented with several options in a column on the left edge of the screen. Add-Ins is one of the available choices, which, if you select it, presents you with the screen shown in Figure B.10. I selected Add-Ins and the screen in Figure B.10 appeared with Analysis ToolPak highlighted in the upper group of choices. When you select this option (you might need to restart Excel to give it a chance to add), you should be 5 MAC users may not have access to the Data Analysis features since they were removed in previous versions. There may be programs available that perform similar functions, but refer to the Excel website for assistance.
USING STATISTICAL FUNCTIONS 541 able to find the Data Analysis submenu on the right side of the Data menu. This will allow you to use the statistical functions we discuss in the book. Review and View Menus These two tabs available from the main screen have useful menus and functions for data management and appearance. I will make reference to them as we encounter them in later chapters. USING STATISTICAL FUNCTIONS The heart of the statistical uses of Excel is in the Data Analysis submenu shown in Figure B.9. I introduce many of these statistical tools in the book chapters describing different statistical procedures. However, before we delve into those specific topics, I want to point out other ways that we can build statistical formulas directly into the spreadsheet. I described several ways in the Formulas section earlier that users can enter statistical formulas directly from the available submenus. As I mentioned, there are several statistical formulas available that we use extensively in this book. Most are single procedure formulas like calculating AVERAGE or STDEV (standard deviation). Other procedures are more complex like the FTEST that calculates the equivalence in variance in two sets of data. Entering Formulas Directly A very important use of Excel is to embed formulas directly into the worksheet so that you can devise whatever calculation you need. The functions we discussed earlier are simply common calculations that have been arranged so that if you have repeated need for a certain calculation, you can use them more quickly than entering the formulas manually. Selecting the = key in any cell notifies Excel that what follows is a user-created formula. Thereafter, you can enter the calculation you want as a string of characters. For example, using the sample of GENHLTH and SEX values shown in Figure B.5, the following commands (user-created formulas) would yield the average value for GENHLTH scores: =Sum(A2:A15)/14. Figure B.11 shows how this looks in Excel. In this example, there are three main components of the formula: = informs Excel that the user is entering a formula. Sum(A2:A15) calls for adding the values together from cell A2 to A15. /14 divides the summed GENHLTH scores by 14 (the total number of scores), yielding the average GENHLTH score (2.214). The results of entering the formula are shown in cell F4 in Figure B.11 (or whatever cell you used to enter the formula). The formula you entered is shown in the
542 EXCEL BASICS Figure B.11 Entering user-generated formulas in Excel. formula bar directly above the spreadsheet. As you can see, it appears exactly as I described earlier. The answer of the formula appears in the cell selected (F4 in the example in Figure B.11). You can edit this formula line if you wish to include additional cases, and the formula will automatically adjust the calculation to reflect the change in values. There are several ways to get the same result for most formulas you might wish to enter. For example, you could use the menu system I described earlier to enter a function to create the AVERAGE, which is what we did using our own formula. Look at Figure B.3 again, and you will see that AVERAGE (listed in the column on the left side of the screen) is one of the choices from the Functions menu. Using the SUM Button Another way to help create your own formulas is to use the button shown on the Home tab at the far right of the menu ribbon. Look at Figure B.5 and you will see this symbol at the right side of the figure. The symbol means sum of, and we will use it extensively in our discussion in later chapters since it is such an important function for statistical analyses. Figure B.12 shows the result of clicking this symbol when the cursor is in cell F6. As you can see, when you select the symbol, it creates a formula calling for summing a series of cells you select in the spreadsheet (shown in a dashed box around the selected values). In the example that follows, I selected the
DATA ANALYSIS PROCEDURES 543 Figure B.12 Using the button to create a formula. string of GENHLTH values (cells A2 A15) with the cursor, which Excel then added to the formula. Figure B.12 also shows a ScreenTip box that appears when you choose the button. Directly below the selected cell where the formula is entered, you will see the help bar explanation of the function: SUM(number1,[number2, ). This shows that the sum symbol enters the SUM function wherein the numbers from the selected cells are added sequentially. Iusedthe button in this example to demonstrate that it is helpful if you are building your own formula. Had we wanted to complete the formula for the average value of the GENHLTH values, we would simply place the /14 figure at the end of the SUM function listed in the formula window. This would create the same formula we created directly shown in Figure B.11. DATA ANALYSIS PROCEDURES The Data Analysis submenu is a more comprehensive and extensive list of statistical procedures available in Excel. Typically, this involves several related and linked functions and specialized formulas that statisticians and researchers use repeatedly. These are more complex than each separate function (e.g., average, standard deviation, etc.) and in fact may use several functions in the computation of the formulas. We start the book showing Descriptive Statistics (a Data Analysis submenu choice)
544 EXCEL BASICS and then move to several inferential procedures also represented in the submenu (e.g., t test, correlation, ANOVA, regression, etc.). MISSING VALUES AND 0 VALUES IN EXCEL ANALYSES Some Excel procedures you use may encounter difficulty if you are using large data sets or have missing cases. In particular, you need to be careful about how to handle missing cases and zeros. Some procedures do not work well with missing values in the data set. Also, be careful about how 0 values are handled. Remember missing cases are not 0 values, and vice versa. USING EXCEL WITH REAL DATA Over the book chapters, I introduce you to several databases that we use to understand the different statistical procedures. I find that it is always better to use real-world data when I teach statistics since students and researchers must, at some point, leave the classroom and venture into situations calling for the use of statistical procedures on actual research problems. I take this same approach in my book Understanding Educational Statistics (Abbott, 2011) in which I demonstrate the use of several statistical procedures using data from actual databases and/or my own evaluation data.