Normality and Sample Size Do Not Matter for the Selection of an Appropriate Statistical Test for Two-Group Comparisons

Methodology ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 61-71 ◽  
Author(s):  
Antoine Poncet ◽  
Delphine S. Courvoisier ◽  
Christophe Combescure ◽  
Thomas V. Perneger
Keyword(s):  
Sample Size ◽  
Test Performance ◽  
Permutation Test ◽  
Bimodal Distribution ◽  
Error Rates ◽  
T Test ◽  
Sample Sizes ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Selection Of

Abstract. Many applied researchers are taught to use the t-test when distributions appear normal and/or sample sizes are large and non-parametric tests otherwise, and fear inflated error rates if the “wrong” test is used. In a simulation study (four tests: t-test, Mann-Whitney test, Robust t-test, Permutation test; seven sample sizes between 2 × 10 and 2 × 500; four distributions: normal, uniform, log-normal, bimodal; under the null and alternate hypotheses), we show that type 1 errors are well controlled in all conditions. The t-test is most powerful under the normal and the uniform distributions, the Mann-Whitney test under the lognormal distribution, and the robust t-test under the bimodal distribution. Importantly, even the t-test was more powerful under asymmetric distributions than under the normal distribution for the same effect size. It appears that normality and sample size do not matter for the selection of a test to compare two groups of same size and variance. The researcher can opt for the test that fits the scientific hypothesis the best, without fear of poor test performance.

scholarly journals Comparison of statistical methods for analysis of small sample sizes for detecting the differences in efficacy between treatments for knee osteoarthritis

2020 ◽  
Author(s):  
Chia-Lung Shih ◽  
Te-Yu Hung
Keyword(s):  
Knee Osteoarthritis ◽  
Sample Size ◽  
Statistical Methods ◽  
Statistical Power ◽  
Permutation Test ◽  
Small Sample Size ◽  
Small Sample ◽  
T Test ◽  
Sample Sizes ◽  
Knee Oa

Abstract Background A small sample size (n < 30 for each treatment group) is usually enrolled to investigate the differences in efficacy between treatments for knee osteoarthritis (OA). The objective of this study was to use simulation for comparing the power of four statistical methods for analysis of small sample size for detecting the differences in efficacy between two treatments for knee OA. Methods A total of 10,000 replicates of 5 sample sizes (n=10, 15, 20, 25, and 30 for each group) were generated based on the previous reported measures of treatment efficacy. Four statistical methods were used to compare the differences in efficacy between treatments, including the two-sample t-test (t-test), the Mann-Whitney U-test (M-W test), the Kolmogorov-Smirnov test (K-S test), and the permutation test (perm-test). Results The bias of simulated parameter means showed a decreased trend with sample size but the CV% of simulated parameter means varied with sample sizes for all parameters. For the largest sample size (n=30), the CV% could achieve a small level (<20%) for almost all parameters but the bias could not. Among the non-parametric tests for analysis of small sample size, the perm-test had the highest statistical power, and its false positive rate was not affected by sample size. However, the power of the perm-test could not achieve a high value (80%) even using the largest sample size (n=30). Conclusion The perm-test is suggested for analysis of small sample size to compare the differences in efficacy between two treatments for knee OA.

scholarly journals PERBEDAAN PENGARUH EFEK AKUT INSTRUMENT ASSISSTED SOFT TISSUE MOBILIZATION (IASTM) DAN SELF MYOFASCIAL RELEASE (SMFR) UNTUK MENINGKATKAN FLEKSIBILITAS OTOT HAMSTRING

2019 ◽  
Vol 3 (2) ◽  
pp. 9-23
Author(s):  
Wijianto . ◽  
Nizar Wazdi
Keyword(s):  
Soft Tissue ◽  
Range Of Motion ◽  
T Test ◽  
Myofascial Release ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Soft Tissue Mobilization ◽  
Paired T Test

Latar Belakang:  Instrumen Assisted Soft Tissue Mobilization (IASTM) merupakan prosedur terapi yang mana menggunakan instrumen untuk secara mekanik menstimulus struktur jaringan lunak untuk mengurangi nyeri otot, ketidaknyamanan, dan meningkatkan secara keseluruhan mobilitas dan fungsi Self Myofascial Release (SMFR) merupakan salah satu teknik manual terapi dengan cara memberikan tekanan pada otot dan fascia yang bertujuan untuk menambah Range of Motion (ROM), mengurangi nyeri, dan meningkatkan fungsi. Tujuan: Tujuan dari penelitian ini adalah untuk mengetahui efek akut perubahan fleksibilitas otot hamstring setelah diberikan IASTM dan SMFR, juga mengetahui adanya perbedaan efek akut antara pemberian IASTM dan SMFR pada perubahan fleksibilitas otot hamtring. Metode: Penelitian eksperimen dengan membandingan pre dan post tes dari dua kelompok yang berbeda perlakuan. Kelompok pertama diberikan perlakuan teknik IASTM, kelompok kedua diberikan perlakuan SMFR.  Data yang dikumpulkan dianalisa menggunakan paired t-test dan mann-whitney test. Hasil: Hasil penelitian menunjukkan efek akut IASTM terhadap fleksibilitas otot hamstring (p = 0,001), efek akut SMFR terhadap fleksibilitas otot hamstring  (p = 0,000), Perbedaan pengaruh antara passive dan active MFR terhadap ketegangan otot (p = 0,134). Kesimpulan: Terdapat peningkatan fleksibilitas otot hamstring pada grup 1 dan grup 2. Tidak ada beda pengaruh yang signifikan antara pemberian IASTM atau SMFR terhadap fleksibilitas otot hamstring.  Kata Kunci: Hamstring, instrumen assisted soft tissue mobilization, fleksibilitas, self  myofascial release.

scholarly journals PENGARUH MENYIKAT GIGI DENGAN SIWAK (Salvadora persica) TERHADAP pH SALIVA

2016 ◽  
Vol 4 (1) ◽  
pp. 45-54
Author(s):  
Yossy Juliarni ◽  
Gunawan Gunawan2
Keyword(s):  
T Test ◽  
Control Group ◽  
Case Group ◽  
Salvadora Persica ◽  
Control Group Design ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Significant Difference ◽  
Salivary Ph ◽  
Paired T Test

Background: Salivary pH is one of factor which involved in caries development. Decreasing of salivary pH will cause enamel demineralization. Miswak (Salvadora persica) as a toothbrush because it has mechanical and chemical effects such as essential oil and bicarbonate which can stimulate salivary secretion. Thus, it will increase the buffer capacity and salivary pH lead to enamel remineralization. Objective: This study aimed to know the effect of toothbrushing with miswak (Salvadora persica) on salivary pH. Methods: The clinical experiment study with pre-test and post-test control group design. The sample of this study is the students of Faculty of Dentistry, Andalas University, Padang. There are 34 students that divided into two groups randomly that is case and control group. Case group used miswak while control group used conventional toothbrush, respectively brushing horizontally for 2 minutes. Salivary pH was measured using digital pH meter in scale of 0.0 to 14.0 with 0.1 sensitivity from pen type pH meter. The data analyzed by Shapiro-Wilk test continued by paired t-test and Mann-Whitney test. Results: paired t-test produced significant value p=0,001 in case group and p=0,000 in control group. Mann-Whitney test produced significant value p=0.317. There was no significant difference in statistic among these groups. Conclusion: Toothbrushing with miswak has effect on salivary pH. Miswak as effective as toothbrush on salivary pH Keywords:Toothbrushing, miswak (Salvadora persica), Salivar

scholarly journals ANALISIS PERBANDINGAN KINERJA KEUANGAN BANK PEMERINTAH (BUMN) DAN BANK UMUM SWASTA NASIONAL (BUSN) DENGAN MENGGUNAKAN METODE PENDEKATAN RGEC (RISK PROFIL E,GOOD CORPORATE GOVERNANCE, EARNING AND CAPITAL)YANG TERDAFTAR DI BURSA EFEK INDONESIA TAHUN 2014-2018

2021 ◽  
Vol 9 (1) ◽  
pp. 127
Author(s):  
Debby Suciani ◽  
Yulita Triadiarti
Keyword(s):  
Corporate Governance ◽  
Risk Profile ◽  
T Test ◽  
Capital Adequacy ◽  
Return On Equity ◽  
Purposive Sampling ◽  
Whitney Test ◽  
Good Corporate Governance ◽  
Mann Whitney Test ◽  
Capital Adequacy Ratio

ABSTRAK Penelitian ini bertujuan untuk menguji apakah terdapat perbedaan kinerja keuangan yang signifikan antara bank pemerintah (BUMN) dengan Bank Umum Swasta Nasional (BUSN) di Bursa Efek Indonesia tahun 2014-2018. . Kinerja keuangan diukur dengan menggunakan metode pendekatan RGEC yaitu Risk Profile, Good Corporate Governance, Earning, and Capital. Aspek Risk Profile diukur menggunakan rasio Non Performing Loan (NPL),aspek Good Corporate Governance diukur menggunakan nilai komposit GCG, aspek Earning diukur menggunakan rasio Return on Equity (ROE), dan aspek Capital diukur menggunakan Capital Adequacy Ratio (CAR). Populasi dalam penelitian ini adalah seluruh bank yang terdaftar di Bursa Efek Indonesia (BEI) tahun 2014 - 2018. Dari 42 perbankan yang terdaftar, dipilih 4 bank pemerintah (BUMN) dan 4 Bank Umum Swasta Nasional dengan menggunakan purposive sampling. Data yang digunakan dalam penelitian ini adalah data sekunder, yang diperoleh dari situs www.idx.co.id, www.ojk.go.id, dan www.bi.go.id. Teknik analisis data yang digunakan adalah analisis deskriptif kuantitatif, uji normalitas, Independent Sample T-test dan Mann Whitney Test. Hasil penelitian menunjukkan bahwa terdapat perbedaan kinerja keuangan yang signifikan antara bank pemerintah (BUMN) dan Bank Umum Swasta Nasional (BUSN) dilihat dari aspek Earning yang diukur dengan rasio Return on Equity (ROE). Dan tidak terdapat perbedaan kinerja keuangan yang signifikan antara bank pemerintah (BUMN) dan Bank Umum Swasta Nasional (BUSN) jika dilihat dari aspek Risk Profile yang diukur dengan rasio Non Performing Loan (NPL), aspek Good Corporate Governance yang diukur dari nilai komposit GCG, dan aspek Capital yang diukur dengan Capital Adequacy Ratio (CAR). Kata Kunci : Perbandingan, Kinerja Keuangan, Non Performing Loan, Nilai Komposit GCG, Return on Equity, dan Capital Adequacy Ratio. 

Type I Error Rates for Welch’s Test and James’s Second-Order Test Under Nonnormality and Inequality of Variance When There Are Two Groups

1994 ◽  
Vol 19 (3) ◽  
pp. 275-291 ◽  
Author(s):  
James Algina ◽  
T. C. Oshima ◽  
Wen-Ying Lin
Keyword(s):  
Degrees Of Freedom ◽  
Type I Error ◽  
Total Sample ◽  
Error Rates ◽  
Second Order ◽  
T Test ◽  
Type I ◽  
Sample Sizes ◽  
Unequal Variances ◽  
Type I Error Rates

Type I error rates were estimated for three tests that compare means by using data from two independent samples: the independent samples t test, Welch’s approximate degrees of freedom test, and James’s second-order test. Type I error rates were estimated for skewed distributions, equal and unequal variances, equal and unequal sample sizes, and a range of total sample sizes. Welch’s test and James’s test have very similar Type I error rates and tend to control the Type I error rate as well or better than the independent samples t test does. The results provide guidance about the total sample sizes required for controlling Type I error rates.

scholarly journals Pengaruh Pemberian Monosodium Glutamat peroral terhadap Degenerasi Neuron Piramidal CA1 Hipokampus pada Tikus Wistar

2013 ◽  
Vol 1 (3) ◽  
Author(s):  
Halomoan Simon ◽  
Hexanto Muhartomo ◽  
Dwi Pudjonarko
Keyword(s):  
T Test ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Post Hoc ◽  
Per Oral ◽  
Paired T Test

Latar belakang : Monosodium glutamat (MSG) adalah garam sodium dari asam amino asam glutamat digunakan luas di masyarakat sebagai penyedap rasa. Pemakaian MSG dalam dosis tepat relatif aman. Penggunaan MSG dalam dosis tinggi dan berlangsung lama menyebabkan gangguan neuroendokrin dan degenerasi neuron, sehingga muncul pertanyaan seberapa jauh MSG peroral berpengaruh terhadap degenerasi neuron piramidal di regio CA1 hipokampus. Tujuan penelitian ini adalah membuktikan pengaruh pemberian MSG peroral terhadap degenerasi neuron piramidal di regio CA1 hipokampus pada tikus Wistar. Metode: Penelitian eksperimental laboratorik dengan 30 tikus Wistar jantan usia 8 minggu, berat 200 gram dibagi menjadi 5 kelompok (1 kelompok kontrol, 4 kelompok perlakuan) diberikan MSG secara oral dosis 5 mg/grBB/hr dan 10 mg/grBB/hr selama 4 minggu. Setelah 2 minggu dan 4 minggu perlakuan dilakukan pemeriksaan patologi anatomi di jaringan hipokampus dan rerata jumlah sel piramidal yang berdegenerasi pada CA1 hipokampus dianalisa dengan Uji ANOVA dilanjutkan Post Hoc, Kruskal Wallis Test dilanjutkan Mann-Whitney Test, uji Paired T-Test dan Wilcoxon Signed Ranks Test. Analisa data menggunakan program SPSS versi 17.0. Hasil: Ada perbedaan bermakna pada rerata jumlah neuron piramidal yang berdegenerasi di regio CA1 hipokampus antara kelompok penelitian setelah 2 minggu dan 4 minggu perlakuan (p=0,0001). Simpulan: Pemberian MSG per oral dosis 5 mg/grBB/hr dan 10 mg/grBB/hr selama 2 minggu dan 4 minggu terbukti berpengaruh terhadap rerata jumlah neuron piramidal yang berdegenerasi di region CA1 hipokampus tikus Wistar. Kata kunci: Monosodium glutamat, degenerasi neuron piramidal CA1 hipokampus.  

scholarly journals Comparison of Motor Skills and Postures of Elite Male Teenage Volleyball and Basketball Players

2021 ◽  
Vol 6 (4) ◽  
pp. 226-239
Author(s):  
Ali Fatahi ◽  
◽  
Behshad Panjehzadeh ◽  
Zahrah Koreli ◽  
Haniyeh Zehtab Asghari ◽  
...  
Keyword(s):  
Motor Skills ◽  
T Test ◽  
The Body ◽  
Basketball Players ◽  
Cross Sectional ◽  
Statistical Population ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Significant Difference ◽  
Volleyball Players

Objective: To achieve the excellent levels of athletic performance, professional athletes need to do continuous exercises and strengthen special muscles of the body and have to spend a lot of time training in that sport. As a result, depending on the prevailing condition of each sport, the physical orientation and the degree of abnormalities of the athletes in that sport are affected. Methods: The current study is descriptive and cross-sectional. The statistical population was 12-14 years old boys in middle and high school. The statistical sample of this study included 30 people (13 volleyball players and 17 basketball players) with a targeted training rate of at least three sessions per week. The Chippaux Smirak Index (CSI) method was used to evaluate the arch of the foot and to determine the angles and degrees of kyphosis and lordosis in radiographs. Independent t-test and Mann-Whitney test were used to compare the variables of motor skills and posture by SPSS V. 18 at a significant level of 0.05. Results: The results of independent t-test to compare the variables of motor skills in the two groups of volleyball and basketball show that there is a significant difference between the two groups in the Sargent test and 4mX9m (P=0.000) (P≥0.05). The results were different in strength test (P=0.41) and Sit-up (P=0.75) so that there was no significant difference between the two groups (P≥0.05). The results of Mann-Whitney test to compare posture-related variables showed that there was no significant difference between the two groups in any of the parameters of varus, valgus, pronation, supination, lordosis, kyphosis, foot flat (P≥0.05). Conclusion: The results showed that volleyball players have more impressive and explosive power than basketball players, but in terms of muscle strength and endurance, there is not much difference between these two groups, which is probably due to the nature and specific characteristics of their sports. Therefore, it seems necessary to pay more attention to athletes’ training programs to improve their motor skills and physical condition. In this study, the behavior and common habits of the subjects in interaction with the environment and hereditary characteristics have not been studied, so more research is needed in the etiology of musculoskeletal abnormalities.

scholarly journals PENGARUH PEMBERIAN ANGKAK (RED YEAST RICE) TERHADAP KADAR GLUKOSA DARAH PUASA PADA WANITA PREDIABETES

2013 ◽  
Vol 2 (4) ◽  
pp. 531-538
Author(s):  
Afina Rachma Sulistyaning ◽  
Yekti Wirawanni
Keyword(s):  
T Test ◽  
Test Design ◽  
Red Yeast Rice ◽  
Purposive Sampling ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Post Test ◽  
Food Recall ◽  
True Experiment ◽  
Paired T Test

Latar Belakang : Manajemen DM efektif dilakukan pada tahap awal sebelum timbul gejala atau prediabetes. Prediabetes ditandai dengan kadar glukosa darah puasa (GDP) mencapai 100 - 125 mg/dl. Angkak merupakan beras hasil fermentasi oleh kapang Monascus purpureous yang dikaitkan dengan perbaikan toleransi glukosa dan penurunan kadar glukosa darah. Penelitian ini bertujuan untuk membuktikan pengaruh pemberian angkak terhadap kadar GDP pada wanita prediabetes.  *)Penulis Penanggungjawab Metode : Jenis penelitian adalah true experiment dengan pre test-post test design. Subjek penelitian adalah karyawati kantor BPPT, Bappeda, BPS, dan yayasan Pangudi Luhur Kota Semarang yang diambil secara purposive sampling sebanyak 28 orang dan dibagi menjadi 2 kelompok secara simple randomization. Kelompok perlakuan diberi angkak 5,4 gram selama 14 hari, sedangkan kelompok kontrol diberi air filtrasi beras sangrai. Pengukuran kadar GDP dilakukan sebelum dan setelah intervensi dengan metode spektrofotometri. Asupan makan subjek sebelum intervensi diperoleh dengan metode food recall 3x24 jam dan selama intervensi dengan metode food recall 5×24 jam. Analisis statistik menggunakan Independent sample t-test, Mann-Whitney test, Paired t-test, korelasi dan regresi linear. Hasil : Kelompok perlakuan mengalami penurunan kadar GDP yang bermakna (p=0.006) sebesar 9.14±10.48 mg/dl sedangkan kelompok kontrol mengalami peningkatan sebesar 1.35±7.39 mg/dl. Secara statistik, terdapat perbedaan perubahan kadar GDP antara kelompok perlakuan dan kontrol yang bermakna (p=0.005).Simpulan : Terdapat penurunan kadar GDP yang bermakna setelah pemberian 5,4 mg angkak selama 14 hari.

scholarly journals Pengaruh Menyikat Gigi dengan Siwak (Salvadora Persica) Terhadap pH Saliva

2020 ◽  
Vol 8 (1) ◽  
pp. 49-56
Author(s):  
Yossy Juliarni ◽  
Gunawan Gunawan
Keyword(s):  
T Test ◽  
Control Group ◽  
Case Group ◽  
Salvadora Persica ◽  
Control Group Design ◽  
Whitney Test ◽  
Mann Whitney Test ◽  
Significant Difference ◽  
Salivary Ph ◽  
Paired T Test

Background: Salivary pH is one of factor which involved in caries development. Decreasing of salivary pH will cause enamel demineralization. Miswak (Salvadora persica) as a toothbrush because it has mechanical and chemical effects such as essential oil and bicarbonate which can stimulate salivary secretion. Thus, it will increase the buffer capacity and salivary pH lead to enamel remineralization. Objective: This study aimed to know the effect of toothbrushing with miswak (Salvadora persica) on salivary pH. Methods: The clinical experiment study with pre-test and post-test control group design. The sample of this study is the students of Faculty of Dentistry, Andalas University, Padang. There are 34 students that divided into two groups randomly that is case and control group. Case group used miswak while control group used conventional toothbrush, respectively brushing horizontally for 2 minutes. Salivary pH was measured using digital pH meter in scale of 0.0 to 14.0 with 0.1 sensitivity from pen type pH meter. The data analyzed by Shapiro-Wilk test continued by paired t-test and Mann-Whitney test. Results: paired t-test produced significant value p=0,001 in case group and p=0,000 in control group. Mann-Whitney test produced significant value p=0.317. There was no significant difference in statistic among these groups. Conclusion: Toothbrushing with miswak has effect on salivary pH. Miswak as effective as toothbrush on salivary pH. Keywords:Toothbrushing, miswak (Salvadora persica), Salivar

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