Concept, How to Run, Interpret, and Report Mann Whitney U Test Show
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Concept of Mann Whitney U TestThe Mann–Whitney U test is the non-parametric alternative to the Independent-samples t-test. The test is used to test for differences between two independent groups on ordinal data or non-normal continuous data. Instead of comparing the means of the two groups, as in the case of the t-test, the Mann-Whitney U Test compares medians. It then evaluates whether the ranks for the two groups differ significantly. As the scores are converted to ranks, the actual distribution of the scores does not matter. Following are a few scenarios in which you could use the Mann-Whitney U test
ExampleThe Problem: To identify if there exists a difference in Service Quality between Supplier and Customer Hypothesis H1: There are significant differences in perception of Service Quality between Supplier and Customer Information Required
Steps to run Mann Whitney U TestStep 1: Go to Analyze → Nonparametric Tests → Legacy Dialogs → 2 Independent Samples Step 2: The resulting dialog box is shown in Figure Step 3: Two-Independent-Samples Test dialog box is displayed, asking for the Test Variable (Service Quality) and Grouping Variable (Type). Add the respective variables into the desired boxes. Step 4: Once the Grouping Variable Gender is added, Click Define Groups, Add 1 (Supplier) into Group 1 box and add 2 (Customer) into Group 2 box and Press Continue. Note. If you are unable to click on the Define Groups Button, first select the Grouping Variable Box. Step 5: Make sure Mann-Whitney U checkbox is selected. The final dialog box should look like one in figure Step 6: Now Press OK Interpreting Mann Whitney U TestThe results shows a number of values, we as research students do not need to look at each and every value, main values of interest include Z value and the Asymp.Sig. (2-tailed). In the results of above example the Z-value is -2.600 and p-value is .009 which is less than .05 and hence we will reject the null hypothesis. There are significant differences in service quality perceptions between supplier and customer. In case one finds a significant differences between groups, you need to describe the direction of the difference (which group is higher). This can be seen from the Ranks table under the column mean rank however when you are presenting your results it is important that median values for each group are reported. This is not available in the test, for this you will have to follow the following procedure. Finding Median for Each Group
Find Median for Each Group
Table 1 shows the case processing summary. The table of interest is table 2. The results shows median value of 2 for Service Quality for both Supplier and Customer. Effect Size Calculation for Mann Whitney U TestSPSS doesn’t provide an effect size statistic, but the value of z that is reported in the output be used to calculate an approximate value of r. r = Z/√N Where Z is the Z Statistics and N is number of cases. For our example value of Z is 2.600 and N is 304, the value of r can be calculated as follows r = 2.600/√304 r = 2.600/17.435 r = 0.14 According to Cohen (1988) criteria .1 = Small Effect, .3 = Medium Effect, and .5 = Large Effect. In this scenario, the effect size is small. Reporting Mann Whitney U TestThe Problem: To identify if there exists significant differences in Service Quality offered to Supplier and Customer Hypothesis H1: There are significant differences in perception of Service Quality between Supplier and Customer To evaluate the difference between Supplier and Customer for Service Quality, Mann-Whitney U Test was utilized. The test revealed significant differences in the Service Quality perception of Suppliers (Median = 2, n = 158) and Customer (Median = 2, n = 146), U = 9711, z = 2.600, p = .009, r = .14. Hence, H1 was supported. Step by Step Video Tutorial on Mann Whitney U TestOther SPSS Tutorials
Langkah langkah uji Mann Whitney dengan SPSS?Cara Uji Mann Whitney di SPSS
Masuk ke menu Analyze, lalu klik secara berurutan Nonparametric Tests, Legacy Dialogs, 2 Independent Samples. Isikan Test Variable List dan Grouping Variable pada kotak dialog Two-Independent-Sample Test dan beri tanda centang pada Mann-Whitney U.
Uji Mann Whitney menggunakan skala data apa?Berdasarkan definisi di atas, uji Mann Whitney U Test mewajibkan data berskala ordinal, interval atau rasio. Apabila data interval atau rasio, maka distribusinya tidak normal.
Apa syarat untuk bisa menggunakan uji Mann Whitney?Syarat Uji Mann Whitney. Data sampel tidak berdistribusi normal.. Dua Kelompok sampel yang saling independent atau tidak berhubungan / tidak berpengaruh satu sama lain (anggota sampel dua kelompok berbeda). Sampel berskala data ordinal, atau interval.. Jumlah sampel pada kedua kelompok sama.. Apa itu uji Wilcoxon dan uji Mann Whitney?Mann-Whitney U test atau Mann-Whitney-Wilcoxon digunakan untuk mengevaluasi apakah median pada dua kelompok berbeda. Untuk melakukan uji Mann-Whitney U, setiap kasus harus memiliki skor pada dua variabel, variabel pengelompokan (variabel independen atau kategoris) dan variabel tes (variabel dependen atau kuantitatif).
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