introduction to spss RESEARCH METHODS & STATISTICS HANDBOOK PHẦN 6 ppsx

51 Go to Edit, Replace and change O into Observed and then E into Expected. Make sure you click on More and check that the „Find Whole Words Only‟ box is checked. Note that if you had not selected the table, Word would have changed everything in the document. As you can see, the columns are no longer wide enough. Select the table and go to Table, Cell Height and Width and change it to something suitable. Try at least one inch. Now try formatting the table. Just as with Excel, you must select the line you want and then add the bordering. The slow way to do that is to go to Format, Borders and Shading each time. The fast way to do it is to use the borders icon in toolbar at the top of your screen. Now select the top row. Point to the left of the word „OBSERVED‟, so that the insertion point turns into an arrow. Click, and the row is selected. Put a ¾ point line on the bottom of the row, and change the line width option to a 2¼ point line for the top of the row. (By the way, to put in special characters like ½ or  go to Insert, Symbol and then choose what you want. While we‟re on the subject, to put an equation into Word, go to, Insert, Object „Microsoft Equation 3.0‟. Play with it, if you want). Returning to the table. On the bottom row, put in a 2¼ point line. To insert a column select the OBSERVED column by pointing above the word OBSERVED until it changes to a black arrow, then click. Now using the right mouse button, insert a column. Enter in the information, as given on the spreadsheet. It is also possible to vertically centre text, such as the table, by going to File, Page Setup, Layout and changing vertical alignment to centre. You might need to go to File, Print Preview or Page Layout view in order to see the full effects. If the table sticks out over the edge of the page. Select the table and autofit it from Table, Cell Height and Width, Column. As you can see, the titles are now too big. You can get round that by shrinking the font size or abbreviating the titles. Improvise. Graphics and Arrows Well, actually just arrows. If you need to do a few graphic bits in Word, such as arrows and boxes, your best bet is do use the Drawing facility. Turn the Drawing toolbar on in a similar way to turning on the Borders toolbar. Type the return key a few times under the table. This now allows us to enter freeform text using the Drawing facility. Click on text box, towards the left of the toolbar. Now drag an area under the table and type the text into the box. The size and font of the text in the box is formatted in the normal way. Make it 14 point. Double click on the edge of the text box and increase the box to one point and the edge to dashed. Choose fill colour and choose light gray. 52 Now draw an arrow pointing to the last column. Double click on the arrow to change the options such as its width, size of arrowhead etc. Make the arrowhead wider and longer, and make the line 2 points. SOURCE OBSERVED EXPECTED OBSERVED- EXPECTED (OBSERVED- EXPECTED)^ 2 (OBSERVED- EXPECTED)^ 2/EXPECTED OPY 13 8.80 4.20 17.60 2.00 OPN 14 18.20 -4.20 17.60 0.97 OFY 2 6.20 -4.20 17.60 2.84 OFN 17 12.80 4.20 17.60 1.37 Creating Tables in Word To create Tables in Word, go to the point in the document where you want the table inserted and go Table Insert Table You will then be asked how many columns and rows you want. Select the number of each that you want then press the AutoFormat button. This is basically a step by step guide to creating the layout of a table. Selection the options you want and then click the “Continue” button for each dialogue box, until you come to the end. You should then have a table you can add rows/columns to and do all the editing described in the lesson above. Creating Templates So far we have seen how you can format styles to make typing large bodies of text both pretty and functional. But as you have no doubt noticed by now, when you leave a document you also leave the formatting with it. How can you change that? Templates When you open a new document, Word defaults to the normal template. The normal template basically is a document with no formatting and with everything set to default. To make things a little more exciting we have to define a template. Go to File, New and choose template. Go to File, Save As and see how it selects save as document template? Cancel that last command. Now, set up some styles that will be useful for when you eventually come to type up your next few pieces of work. Chi-Square Table 53 Think back to the session where you created those styles. In this template, do the same. You don‟t actually need any text, though it may help if you type in a few lines to show what the different styles actually do. The whole point of doing this is that when you come to do future work, anything saved in the template will be present. So, if you want a standardised title page then create it now, obviously leaving gaps for titles and dates, etc. When you are happy with your template, go to File, Save As. Call it something like „Essays‟ or „Coursework‟. All the styles and any standard text will now be saved as the template. Close the template down, and close Word. Now, when you re-enter Word it still gives you the default „Normal‟ template. Go to File, New and choose the template name and OK. As if by magic, the formatting and styles appear. When you open a new document, several other templates are offered to you. Try opening Elegant Letter.dot. Note the blanks you have to fill in to create quick letter? Other Bits Made a mistake? In Word we undo mistakes by going to Edit, Undo. You can also redo things by going to Edit, Redo. If you had a long list of variables on consecutive lines and wanted to sort them alphabetically (make sure there is a „hard return‟ after each variable, using Edit, Replace if necessary by replacing a space with a hard return from Special Characters), you can select what you want sorted and go to Table, Sort. You can also splice the document into two windows, for those fancy multi-task operations, by using Window, Split and then clicking where you want to have the split. Get rid of it by moving the split into the toolbar. Now, from Tools, choose Spelling and run a spell check. You can also run a Grammar check. Open a document. With that document open, do a word count, from Tools, Word Count. 54 MS Excel Exercises A spreadsheet is a cross between a calculator and a word processor, with a bit of statistical package thrown in. Its main use is in automating repetitive number crunching tasks or for formatting and cleaning data files. A spreadsheet consists of a matrix of rows and columns, each identified by a cell name (its „address‟). As you move around the sheet, you are selecting different cells, and you can type in data and formulae. Entering Data and Using Formulae Your mission today is to copy in the spreadsheet (exactly – including bold print, larger font, border lines, etc.) and learn how to use formulae and names to demonstrate different coefficients. Entering Text Most text is entered just as in Word. Note that if a line is too long for a cell then it will run over the other cells. This usually causes no problems, though it may seem counter-intuitive. Copy the top half of the spreadsheet, and don‟t forget to use formatting. Change the print layout to landscape from File, Page Setup, Landscape. This is very similar to Word. Watch out for the borders - look on the toolbar towards the right hand side. Don't forget to use Edit, Undo if it goes pear-shaped. Don't bother entering the numbers in the second part of the sheet (where it starts with Phi) - these will change later. Do note that the formatting for the coefficients is different - select these four cells and go to Format, Cells, Number and then switch the decimal places to 2. Most of the sheet is text, but some cells are named or are formulae. This is where the fun begins. Names and Formulae Basically, a named cell is one which has a pseudonym. Hence, when referring to a name cell, rather than type in cell addresses, which are not meaningful, we can use names, which are. In the Data Entry Area, name cell D23 as „PP‟ by going to Insert, Name, Define and calling it PP, meaning variable 1 Present and variable 2 Present. Name E23 as „PA‟ etc. See how just under „Arial‟ the cell address changes to the name. 55 Formulae are used in cells to perform calculations. If you type in the formula then the coefficients will change automatically as you change the data entry area. Hence you can see for example how joint non-occurrence is not used by Jaccard‟s, even the figure is huge compared to the rest. A formula always starts with an „=„ sign. So, in cell G24 (named „Sum‟) the line should be „=PP+AP+PA+AA‟. If you enter data into the named cells in the data entry area, you will see that the Sum automatically changes. The Formulae If we weren‟t using names, the formula for Jaccard‟s would be =D23/(D23+D24+E23). Note the use of brackets - this is highly important but not very useful. Using the names created earlier, you can now type into cell C33 the formula =PP/(PP+AP+PA). This is more meaningful, and emphasises the simplicity of Jaccard‟s as well as the fact that it ignores joint non-occurrence (i.e. AA). Provided there are values in the data entry area, Jaccard‟s coefficient will be calculated instantly. Try entering the formulae for the other coefficients. These are: Phi AA PP AP PA AA AP AA PA PP AP PP PA       * * ( )*( )*( )*( ) (Looks vaguely familiar? It‟s Pearson‟s dichotomised. Squareroot is achieved by raising to the power of 0.5 i.e. ^0.5) Don‟t forget - careful with those brackets. Testing the Formulae Enter different values into the data entry area and see how the different coefficients give wildly different results. Moral of the story: make sure the coefficient you use is appropriate or risk completely invalid results. Other related questions: What are the effects of the value (e.g. 0, 10 and 1000) of the AA cell on different coefficients? Doing Calculations in Excel Now we take this a stage further and show how formulae are used in more advanced calculations. Since much of this has been done before, the instructions in this exercise will be more brief. 56 We‟re going to investigate the past record of MSc candidates on the exam using the variables result (pass/fail) and bribed examiner (yes/no). To do this we will use chi squares. Contingency Tables Type in the contingency table, then select it all and copy it further down the page to make the observed table. Careful of the formatting. Numbers should be changed by Format, Cells, Number, and setting decimal places to 2. Borders are Format, Cells, Border (or you can use the borders icon from the tool bar). Note that in the observed table, the values are called various names. Remember, that‟s Insert, Name, Define. Use formulae to calculate the totals columns, for example the „Yes‟ column is „=OPY+OFY‟, with O standing for observed, P for pass. Got the picture? As you are all aware, the chi squared test examines the observed (i.e. empirically obtained) results with the statistically expected set of results. Clearly if there is a significant difference between observed and expected then there is hypothesised to be some mechanism causing this difference and hence we can conclude that the observed results are not due to chance factors. Chi squared is given by:    Expected ExpectedObserved 2 2 )(  To calculate the statistically expected results, we use probability theory. If you are comfortable with this, then carry on. If not, then check with the textbooks. Note the formulae used to obtain the expected results. For example, expected for pass and yes is pass total multiplied by yes total all divided by the number of observations i.e. „=(Yes*Pass)/Sum‟. Do this for all expected results. Under the values part, put „=OPY‟ under the O column (where the number 13 is), and =„EPY‟ under the E column (where the number 8.80 is). Now type the rest of the numbers into the O and E columns. Under the O-E column, first type '=', then click two cells to the left with the value of OPY in it. Now type '-', and click one cell to the left with the value of EPY in it. Press return. See how it automatically enters the cell address? Select the cell you just typed the formula into and drag down onto the three cells below it. Go to Edit, Fill, Down and the formula will be copied down. Note how the formula changes automatically, relative to where the values are? Do the same for squaring the result and dividing it into E. 57 Manual Chi Square Effort Contingency Table: Bribed Examiner Yes No Total Result Pass OPY OPN Pass Fail OFY OFN Fail Total Yes No Sum Observed: Bribed Examiner Yes No Total Result Pass 13 14 27 Fail 2 17 19 Total 15 31 46 Expected: Bribed Examiner Yes No Result Pass 8.8 18.2 Fail 6.2 12.8 Values: O E O-E (O-E)^2 (O-E)^2/E 13 8.80 4.20 17.60 2.00 14 18.20 -4.20 17.64 0.97 2 6.20 -4.20 17.64 2.85 17 12.80 4.20 17.64 1.38 Chisq.= 7.19 58 For our last trick - to sum, automatically click on the cell where you want the chi square value to go and then on the summation symbol () on the toolbar. Drag over the last column and press return to obtain the sum. The chi square value can be checked with statistics table to judge its significance. Degrees of freedom are given by (r-1) (c-1) i.e. the numbers of rows in the contingency table minus one multiplied by the number of columns in the table minus one. Some Questions For You To Consider What happens if the sample size drops below 45? What if it drops below 5 in any cell? 59 APPENDIX BASIC STATISTICS 60 Basic Statistics A statistic is a structured piece of data, carrying meaningful information. Research begins when we start to investigate these statistics systematically, i.e. to analyse them. Broadly, there are two sorts of statistical analysis:  Descriptive statistics: this involves analysing the parameters of the sample and assessing the characteristics of the population.  Inferential statistics: most often this involves hypothesis testing using a sample to test differences in a population. To begin with, we will concern ourselves with descriptive statistics. Data: Its Collection and Its Disposal So, how do we obtain data? To convert information into data requires some sort of coding framework consisting of variables, or attributes, relating to the domain of concern. People (cases) are sampled representatively so that clues as to the nature of the population can be calculated. Attributes (Variables) 1: 2: 3: 4: 5: Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Issues in Coding Data Issues involved in the choice of content categories:  exhaustivity - ensure all cases are covered by the options or levels in the category  exclusivity - each case must have only one possible option or level in the category  relevance - the item must pertain to the domain of concern  adequate coverage of domain - the domain must be adequately covered  specificity - the definition of each category must be precise to allow for consistent coding (this also relates to inter-rater reliability - more later). This data can be displayed in a number of ways: as percentages, ratios, in a bar chart, cumulative frequency chart, pie chart, etc. Each of these describes the characteristics of the sample, hence the term descriptive statistics. Often these data sources are noisy and hence we must take care in the construction of coding frameworks and we must determine which forms of analysis are feasible. We . way to do that is to go to Format, Borders and Shading each time. The fast way to do it is to use the borders icon in toolbar at the top of your screen. Now select the top row. Point to the. 17 .60 2.00 OPN 14 18.20 -4.20 17 .60 0.97 OFY 2 6. 20 -4.20 17 .60 2.84 OFN 17 12.80 4.20 17 .60 1.37 Creating Tables in Word To create Tables in Word, go to the. numbers into the O and E columns. Under the O-E column, first type '=', then click two cells to the left with the value of OPY in it. Now type '-', and click one cell to the