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# IntroEmpirMthdsPolResearch PSC280

CMU

GPA 3.72

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This 13 page Class Notes was uploaded by Kelsie Koelpin V on Monday October 5, 2015. The Class Notes belongs to PSC280 at Central Michigan University taught by MihaielaGugiu in Fall. Since its upload, it has received 21 views. For similar materials see /class/218913/psc280-central-michigan-university in Political Science at Central Michigan University.

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Date Created: 10/05/15

PSC 280 Mid Term Study Guide I The list of questions is designed to guide you What is the difference between correlation and causation How do the method of difference and the method of agreement differ When would you use one over the other and why How do deductive and inductive reasoning differ How can you recognize when a researcher uses deductive or inductive reasoning check the examples used in class What are the characteristics of a goodstrong research question Why is it important for a research question to have these characteristics What are the component steps of a literature review Why should a researcher conduct a literature review in the first place Why it is important to de ne key terms in a research What definitions can a researcher use to de ne hisher key terms Are some definitions better than others Ifyes why What does operationalization involve What is the difference between random and systematic measurement error What is selection bias and when does it occur What is the difference between probability and nonprobability samples What types of probability samples have we studied What are the similarities and differences among them When would one choose a specific type of probability sampling design e g SRS Think about possible scenarios for each type of sampling design What are the different types of nonprobability sampling discussed in class What are the differences among them When would one use these types of sampling designs What is the goal of observational research What types of observation research are and what are the differences among them What is reliability and how would one estimate it What reliability methods assess intemal consistency Which one of them is better and why What is the difference between a coe ciem of stability and a coe cient of equivalence What does validity refer to What types of validation have we discussed What does each validation method entail e g how would you show that your measureinstrument has content validity What characteristics differentiate the four levels of measurement What statistical ie mathematical operations can one perform at each level of measurement What threats to internal and external validity one should be aware of when choosing a research design What do they mean in practice e g what does history mean What type of preeXperimental experimental and quasiexperimental designs did we discuss in class What are their characteristics What are the threats to internal and or external validity for each type of study design Why is randomization important What is the difference between random selection and random assignment PSC 280 November 23 2010 Homework 5Answ ers Complete the following exercises by hand and make sure to include ALL steps in the homework You can choose to either write legible or type by using the Equation option in Word If you do NOT present every single step of these analyses you will NOT earn al the points 1 Newsweek reported statistics on the number a Visits a couple makes to a therapist while undergoing marriage counseling With data based on this article assume that the following show the number of Visits for a sample of nine couples X 12 8 3 13 18 20 10 9 18 Compute the following descriptive statistics for these data 6 points a Mean 7clle lt1283131820109181233 7111 b Median X3 8 9 10 12 13 18 18 20 Meagan Xn12 X912 X5 12 c Mode 18 d Variance s2 i2x no2 quot 1 11 9i1122 82 32 132 182 202 102 92 182 912332 3075 e Standard deViation S LIZ 402 3o75 555 71 21 f Standard error SEsJZ555J 185 2 The following data have been collected from a sample of8 items X 10 8 12 15 13 11 6 5 Compute the following a Mean 1 points 971le108121513116510 7111 b Standard deviation 1 points 2 1 n 2 2 S x n X n1 K OY 82 122 152 132 112 62 52 8102 1197 S LIZOCl J CY Vll97346 71 21 c 95 con dence interval 5 points 2 itaZSE SE sJZ 346J 1223 Df n1817 T critical value for or 05 is 2365 LB 10 23651223 711 UB 10 23651223 1289 95 CI 711 1289 3 A simple random sample of 20 items resulted in a sample mean of 1725 and a sample standard deviation of 33 Compute the following Note you may get slightly different numbers depending on how you do the rounding However the difference should be very small a 90 confidence interval 5 points SEsJZ33JE738 105 90 CI 1597 1853 b 95 con dence interval 5 points 1025 95 CI 15711880 c 99 con dence interval 5 points toos 2861 99 CI 15141936 4 The following data are family sizes from a simple random sample of households in a new congressional district 2 3 395 6 points zlle lt432245323632325 7111 2 n 2 2 s n1Zx mm 1 42 32 22 22 42 52 32 22 32 62 32 22123252 166 S leocl xy 11661288 71 21 SE sJZ 1288JE 372 Dfn1 121 11 L025 95 CI 243 407 5 A study of educational levels of voters and their political party affiliations showed the following results Party Affiliation not school counts are a Determine whether the relationship between party affiliation and education is statistically signi cant at or 01 8 points E Rowz39 TotalColumn j Total U Grand Total 100 100 Example EDemampCollege Degree 2 40 2 observed exp ected2 ii 01 Ez 2 Z allcells exp eCted 21 1 EU 40 282 30 322 30 402 20 282 35 322 45 402 10 142 15 162 25 202 28 32 40 28 32 40 14 16 20 1342 Df No columns1No rows1 3131 4 For at 01 the critical value of X2 132767 which is smaller than 1342 Hence the relationship is statistically signi cant 6 A new study investigating the relationship between gender and political party affiliation showed the following results Note exactly the same process is used for this problem Party Affiliation 58 50 Total 35 33 40 108 counts are a Determine whether the relationship between party affiliation and gender is statistically signi cant at 01 05 8 points x2 1521 Df 3 12 1 2 For 01 05 critical value of X2 599147 which is larger than 1521 Hence the relationship is NOT statistically signi cant 7 Consider the following hypothesis test H0 p 20 Ha p 75 20 Data from a sample of six items are as follows X 18 20 16 19 17 18 a Compute the mean 1 points 1 YL f x 18 b Compute the standard deviation 1 points 1 S LIZOCZ J CY Vl99l4l 71 21 c Compute the value of the test statistic t 5 points 2 n 2 2 s nlZxl nX 199 E y 18 20 346 sJZ 141J5 t Note that the denominator is the standard error d What is your conclusion 1 point If we assume that 01 05 the critical tvalue for n 1 19 degrees of freedom is 2093 We divide alpha by 2 because the alternative hypothesis does not indicate a direction of the relationship Since 346 is larger than 2093 we can reject the null hypothesis and conclude that the sample mean does not equal 20 8 City Homes bought 101 badly deteriorated Baltimore rowhouses and turned them into housing for the poor The mean monthly rent for these houses was 200 Nine hundred homes in another city were built and turned over to a foundation to rent A sample of 10 of these homes showed the following monthly rental rates 220 190 250 230 185 210 240 260 200 195 a Using 01 05 test to see if the mean monthly rental rate for the population of 900 homes exceeds the 200 mean monthly rental rate in Baltimore 5 points b What is your conclusion 1 point H0u5200 Haugt200 Note that this is a one sided test because the directionality of the relationship I being speci ed by the alternative hypothesis n10 1 71 2l8 x 71ng 2 n 2 2 s n1 xl nX 690112 S LEW icy 6901122627 71 21 Tc y 218 200 2 17 sJZ 2627 l10 t For 9 degrees of freedom the critical tvalue is 1833 which is smaller than 217 Hence we can reject the null hypothesis and conclude that the population mean rental rate exceeds the 200 per month rate in Baltimore 9 Starting salary data for college graduates is reported by the College placement Council Annual salaries in thousands of dollars for a sample of accounting majors and a sample of nance majors are shown below a Using 0L 05 test the hypothesis that there is no difference between the mean annual starting salaries for the populations of accounting majors and finance majors 5 points nAccouming 12 nFimmce 12 H01H112 Haill llz xACCuummg 273 9 CFZVMZYLCE 2L n 2 2 s n1 ltxgt nooj FIIKZSBZ 2532 2622 2792 2702 2622 2812 2472 2522 2922 2972 2932 122732 312 s12 gxf n2428 S n1 1sf n2 1s 12 131212 1428 34324708 P 37 n1n2 2 1212 2 22 Df n1n272 22 t 9 61 970 M 2 273 256 0 2 1 1 J37ii spnn2 12 12 1 222 b What is your conclusion 1 point For 22 degrees of freedom and or 05 the critical value oft is 2074 which is smaller than 222 Hence we can reject the null hypothesis and conclude that there is a statistically signi cant difference between the mean salaries of accounting and finance majors 10 Samples of final examination scores for two research methods classes with different instructors provided the following results Instructor A Instructor B n1 n2 f1 72 E 78 s1 8 s2 10 a Using 0L 05 test the hypothesis that the population mean grades differ for the two groups 5 points H01H1H2 Hawm pz s189s128264 sz109sz2100 S n1 1sfn2 1s 12 16415 1100 7041400 P nln2 2 1215 2 25 8416 t 9 61 C2 Iu2 72 78 0 2 i i J846ii Jspn n2 12 15 1 169 b What is your conclusion 1 point For 25 degrees offreedom the critical value oft is 2060 which is larger than 169 remember the tdistribution is symmetrical Consequently we cannot reject the null hypothesis and we conclude that there is no statistically significant difference between the mean grades of the 2 groups 11 Safegate Foods Inc is redesigning the checkout lanes in its supermarkets throughout the country Two designs have been suggested Tests on customer checkout times have been collected at stores where the two new systems have been installed The sample data are as follows a Using 01 05 determine whether there is a difference between the population mean checkout times for the two systems 5 points Note Because the sample sizes are larger than 30 we must use z s12 222 484 s22 152225 Cl Cl lu1 l2 41 33 0 319 Jo39lZnlo3922n2 J484120225100 The critical 2 score associated with an 01 05 is 196 which is smaller than 319 Hence we can reject the null hypothesis and conclude that the difference it is statistically significant 12 A random sample of 16 observations was selected from each of four populations A portion of the AN OVA table is shown below Source of Sum of Squares Degrees of Mean Square F Variation Freedom Between 1200 3 400 16 Within 300 12 25 Total 1500 15 a Complete the missing entries in the table 5 points DfSSB kl 413 Df SSW nT k 16 74 12 Df Total 3 12 15 MSW nT k Hence SSW MSW nTik 25 12 300 SST SSW SSB 9 SSB SST iSSW 1500 7300 1200 MSB 16 MSW 25 b Using 0L 05 level of significance test the null hypothesis that the means of the four populations are equal What is your conclusion 4 points For 3 degrees of freedom numerator and 12 degrees of freedom denominator F3712 349 which is smaller than the value obtained above ie F 16 Hence we can reject the null hypothesis and conclude that the means of the four populations are not equal 13 Random samples of 25 observations were selected from each of three populations For these data SSB 120 and SSW 216 a Set up and complete the ANOVA table 5 points Source of Sum of Squares Degrees of Mean Square F Variation Freedom Between 120 60 20 Within 216 72 3 Total 336 75 Note there are 3 samples drawn from 3 different populations and each sample has 25 observations DfSSB kl 3l2 Df SSW nT k 75 7 3 72 Df Total 2 72 75 SST 120 216 336 MSBJSB zmz 16 1 2 MSW 2amp23 nT k 72 MSB MSW 3 b At the or 05 level of signi cance what is the critical F value 2 points F 272 307 since the table has values up to 60 df we can use that value to make our decision H c At the or 05 level of signi cance can we reject the null hypothesis that the means of the three populations are equal 2 point Yes we can reject the null hypothesis because 20 is higher than the critical value

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