Week of notes 11
Week of notes 11 400
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This 3 page Class Notes was uploaded by Dora Notetaker on Thursday November 5, 2015. The Class Notes belongs to 400 at University of Alabama at Birmingham taught by John E McNulty in Summer 2015. Since its upload, it has received 21 views. For similar materials see Research in Political Science in Public Relations at University of Alabama at Birmingham.
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Date Created: 11/05/15
PSC 4002D: Research in Political Science Dr. McNulty Set of Notes 11 Week of Nov 2 Tue, Nov. 3 Chi square statistic ● It is used to compare 2 categorical variables ● Like variables that cause countries to go to war with each others International Relations researchers use dyads to compare countries ● For each dyads, they ask 2 questions: ○ Do they share a border ○ Have they been to war with each other ● They put these in a table ● This is our Observed table War No War Border 500 3000 3500 No border 1000 30,000 31,000 1500 33,000 34,500 ● (made up numbers) ● sums on the outside of the table ● We create an Expected table with the same numbers on the outside. War No War Border (Row1/Grand total) (Row1/Grand total) x 35 x Column1 Column2 No (Row2/Grand total) (Row2/Grand total) x 310 border x Column1 Column2 15 330 345 ● And this equals: War No War Border (35/345) x 15 = 1.5 33.5 35 No 13.5 296.5 310 border 15 330 345 ● The sums on the outsides of the graph should be the same as before ● So you could subtract one of the rows ● # of cell you have to work before you don’t have to use multiplication or division is known as degrees of freedom, or df ● df = (# of rows 1) x (# of columns 1) For the Chi square statistic: War No War Border a b No c d border ● a = (51.5)/ 1.5 = 8.2 ● b = (3033.5)2 /33.5 = 0.4 2 ● c = (1013.5) /13.5 = 0.9 ● d = (300296.5)2 /296.5 = 0.0 ● Sum = 8.2+0.4+0.9+0.0 = 9.5 χ2= 9.5 Thurs. Nov. 5 We looked at our sample SPSS table to see how to get the Chi Square Statistic In SPSS, use the following buttons/ tabs to get the Chi square statistic: 1. Analyze tab Descriptive Statistics Crosstabs Choose 2 variables Statistics check the Chi square Continue OK ● When you have the crosstabs window open, be sure to go to Cells, and hit both the Expected and the Observed tabs ● The middle table is the Expected table ● The Chi square Tests table is your results When looking at the Chi square table on the bottom, in the Pearson Chi Square row, the number under Value is your chi square, the df is your degrees of freedom, and the last value in the row is your percentage. ● So if it says .019, it means you are 1.9% likely that the relationship could have happened by random change, so there’s no true relationship. ● So you’re 98.1% confident that there is a relationship between the variables, thereby disproving the Null hypothesis (which says there is no relationship) To select cases you need: Data Select Cases Choose the variable you want Under if, choose what you need OK ● You will see the cases you don’t need in your actual data table with a line through them To compare means: Analyze Compare Means Indep. Samples T Test Choose 2 variables Define Groups, put 0 and 1 hit OK