This article discusses statistical methods for comparing the means of several groups and focuses on examples from 50 Original Articles published in the Journal in 1978 and 1979. Although medical authors often present comparisons of the means of several groups, the most common method of analysis, multiple t-tests, is usually a poor choice. Which method of analysis is appropriate depends on what questions the investigators wish to ask. If the investigators want to identify which of the groups under study are different from the rest, they will need a different method from the one required if they wish simply to decide whether or not the groups share a common mean. More complicated questions about the group means call for more sophisticated techniques. Of the 50 Journal articles examined, 27 (54 per cent) used inappropriate statistical methods to analyze the differences between group means. Investigators need to become better acquainted with statistical techniques for making multiple comparisons between group means.
This article has been cited by other articles:
Freidlin, B., Korn, E. L., Gray, R., Martin, A.
(2008). Multi-Arm Clinical Trials of New Agents: Some Design Considerations. Clin. Cancer Res.
14: 4368-4371
[Abstract][Full Text]
Aslangul, E., Ruimy, R., Chau, F., Garry, L., Andremont, A., Fantin, B.
(2005). Relationship between the Level of Acquired Resistance to Gentamicin and Synergism with Amoxicillin in Enterococcus faecalis. Antimicrob. Agents Chemother.
49: 4144-4148
[Abstract][Full Text]
Schneiders, D., Heger, J., Best, P., Michael Piper, H., Taimor, G.
(2005). SMAD proteins are involved in apoptosis induction in ventricular cardiomyocytes. Cardiovasc Res
67: 87-96
[Abstract][Full Text]
Andries, K., Verhasselt, P., Guillemont, J., Gohlmann, H. W. H., Neefs, J.-M., Winkler, H., Van Gestel, J., Timmerman, P., Zhu, M., Lee, E., Williams, P., de Chaffoy, D., Huitric, E., Hoffner, S., Cambau, E., Truffot-Pernot, C., Lounis, N., Jarlier, V.
(2005). A Diarylquinoline Drug Active on the ATP Synthase of Mycobacterium tuberculosis. Science
307: 223-227
[Abstract][Full Text]
Taimor, G., Schluter, K.-D., Best, P., Helmig, S., Piper, H. M.
(2004). Transcription activator protein 1 mediates {alpha}- but not {beta}-adrenergic hypertrophic growth responses in adult cardiomyocytes. Am. J. Physiol. Heart Circ. Physiol.
286: H2369-H2375
[Abstract][Full Text]
Nuermberger, E. L., Yoshimatsu, T., Tyagi, S., O'Brien, R. J., Vernon, A. N., Chaisson, R. E., Bishai, W. R., Grosset, J. H.
(2004). Moxifloxacin-containing Regimen Greatly Reduces Time to Culture Conversion in Murine Tuberculosis. Am. J. Respir. Crit. Care Med.
169: 421-426
[Abstract][Full Text]
Loureiro-Silva, M. R., Cadelina, G. W., Groszmann, R. J.
(2003). Deficit in nitric oxide production in cirrhotic rat livers is located in the sinusoidal and postsinusoidal areas. Am. J. Physiol. Gastrointest. Liver Physiol.
284: G567-G574
[Abstract][Full Text]
Wolever, T. M., Mehling, C.
(2003). Long-term effect of varying the source or amount of dietary carbohydrate on postprandial plasma glucose, insulin, triacylglycerol, and free fatty acid concentrations in subjects with impaired glucose tolerance. Am. J. Clin. Nutr.
77: 612-621
[Abstract][Full Text]
Glerant, J.-C., Jounieaux, V., Parreira, V. F., Dury, M., Aubert, G., Rodenstein, D. O.
(2002). Effects of Intermittent Negative Pressure Ventilation on Effective Ventilation in Normal Awake Subjects*. Chest
122: 99-107
[Abstract][Full Text]
Yoshimatsu, T., Nuermberger, E., Tyagi, S., Chaisson, R., Bishai, W., Grosset, J.
(2002). Bactericidal Activity of Increasing Daily and Weekly Doses of Moxifloxacin in Murine Tuberculosis. Antimicrob. Agents Chemother.
46: 1875-1879
[Abstract][Full Text]
Schafer, M., Schafer, C., Piper, H. M., Schluter, K.-D.
(2002). Hypertrophic responsiveness of cardiomyocytes to {alpha}- or {beta}-adrenoceptor stimulation requires sodium-proton-exchanger-1 (NHE-1) activation but not cellular alkalization. Eur J Heart Fail
4: 249-254
[Abstract][Full Text]
Kanevskij, M., Taimor, G., Schafer, M., Piper, H. M., Schluter, K.-D.
(2002). Neuropeptide Y modifies the hypertrophic response of adult ventricular cardiomyocytes to norepinephrine. Cardiovasc Res
53: 879-887
[Abstract][Full Text]
Lounis, N., Bentoucha, A., Truffot-Pernot, C., Ji, B., O'Brien, R. J., Vernon, A., Roscigno, G., Grosset, J.
(2001). Effectiveness of Once-Weekly Rifapentine and Moxifloxacin Regimens against Mycobacterium tuberculosis in Mice. Antimicrob. Agents Chemother.
45: 3482-3486
[Abstract][Full Text]
Foda, H. D., Rollo, E. E., Drews, M., Conner, C., Appelt, K., Shalinsky, D. R., Zucker, S.
(2001). Ventilator-Induced Lung Injury Upregulates and Activates Gelatinases and EMMPRIN . Attenuation by the Synthetic Matrix Metalloproteinase Inhibitor, Prinomastat (AG3340). Am. J. Respir. Cell Mol. Bio.
25: 717-724
[Abstract][Full Text]
Friedlaender, M. M., Wald, H., Dranitzki-Elhalel, M., Zajicek, H. K., Levi, M., Popovtzer, M. M.
(2001). Vitamin D reduces renal NaPi-2 in PTH-infused rats: complexity of vitamin D action on renal Pi handling. Am. J. Physiol. Renal Physiol.
281: F428-F433
[Abstract][Full Text]
Kim, Y., Sung, S.-s. J., Kuziel, W. A., Feldman, S., Fu, S. M., Rose, C. E. Jr
(2001). Enhanced Airway Th2 Response After Allergen Challenge in Mice Deficient in CC Chemokine Receptor-2 (CCR2). J. Immunol.
166: 5183-5192
[Abstract][Full Text]
Umpaichitra, V., Bastian, W., Taha, D., Banerji, M. A., AvRuskin, T. W., Castells, S.
(2001). C-peptide and Glucagon Profiles in Minority Children with Type 2 Diabetes Mellitus. J. Clin. Endocrinol. Metab.
86: 1605-1609
[Abstract][Full Text]
Baydur, A., Adkins, R. H., Milic-Emili, J.
(2001). Lung mechanics in individuals with spinal cord injury: effects of injury level and posture. J. Appl. Physiol.
90: 405-411
[Abstract][Full Text]
Hsieh, C.-C., Yen, M.-H., Yen, C.-H., Lau, Y.-T.
(2001). Oxidized low density lipoprotein induces apoptosis via generation of reactive oxygen species in vascular smooth muscle cells. Cardiovasc Res
49: 135-145
[Abstract][Full Text]
Scherzer, P., Nachliel, I., Ziv, E., Bar-On, H., Popovtzer, M. M.
(2000). Effects of variations in food intake on renal sodium pump activity and its gene expression in Psammomys kidney. Am. J. Physiol. Renal Physiol.
279: F1124-F1131
[Abstract][Full Text]
Schafer, M., Frischkopf, K., Taimor, G., Piper, H. M., Schluter, K.-D.
(2000). Hypertrophic effect of selective beta 1-adrenoceptor stimulation on ventricular cardiomyocytes from adult rat. Am. J. Physiol. Cell Physiol.
279: C495-C503
[Abstract][Full Text]
Curran-Everett, D.
(2000). Multiple comparisons: philosophies and illustrations. Am. J. Physiol. Regul. Integr. Comp. Physiol.
279: R1-R8
[Abstract][Full Text]
Taimor, G., Hofstaetter, B., Piper, H.M.
(2000). Apoptosis induction by nitric oxide in adult cardiomyocytes via cGMP-signaling and its impairment after simulated ischemia. Cardiovasc Res
45: 588-594
[Abstract][Full Text]
Schluter, K.-D., Frischkopf, K., Flesch, M., Rosenkranz, S., Taimor, G., Piper, H. M.
(2000). Central role for ornithine decarboxylase in {beta}-adrenoceptor mediated hypertrophy. Cardiovasc Res
45: 410-417
[Abstract][Full Text]
Moss, M., Trow, T. K., Clardy, N.
(1999). Differences in the Response Times of Pages Originating From the ICU. Chest
116: 1019-1024
[Abstract][Full Text]
Candiani, G., Abbondi, M., Borgonovi, M., Romano, G., Parenti, F.
(1999). In-vitro and in-vivo antibacterial activity of BI 397, a new semi-synthetic glycopeptide antibiotic. J Antimicrob Chemother
44: 179-192
[Abstract][Full Text]
Castenmiller, J. J. M., West, C. E., Linssen, J. P. H., van het Hof, K. H., Voragen, A. G. J.
(1999). The Food Matrix of Spinach Is a Limiting Factor in Determining the Bioavailability of ß-Carotene and to a Lesser Extent of Lutein in Humans. J. Nutr.
129: 349-355
[Abstract][Full Text]
Taimor, G, Lorenz, H, Hofstaetter, B, Schluter, K.-D, Piper, H.M
(1999). Induction of necrosis but not apoptosis after anoxia and reoxygenation in isolated adult cardiomyocytes of rat. Cardiovasc Res
41: 147-156
[Abstract][Full Text]
Takaya, J, Teraguchi, M, Nogi, S, Ikemoto, Y, Kobayashi, Y
(1998). Relation between plasma nitrate and mean pulmonary arterial pressure in ventricular septal defect. Arch. Dis. Child.
79: 498-501
[Abstract][Full Text]
Goldberg, Y., Taimor, G., Piper, H. M., Schluter, K.-D.
(1998). Intracellular signaling leads to the hypertrophic effect of neuropeptide Y. Am. J. Physiol. Cell Physiol.
275: C1207-C1215
[Abstract][Full Text]
Carballo, E., Lai, W. S., Blackshear, P. J.
(1998). Feedback Inhibition of Macrophage Tumor Necrosis Factor- Production by Tristetraprolin. Science
281: 1001-1005
[Abstract][Full Text]
Ji, B., Lounis, N., Maslo, C., Truffot-Pernot, C., Bonnafous, P., Grosset, J.
(1998). In Vitro and In Vivo Activities of Moxifloxacin and Clinafloxacin against Mycobacterium tuberculosis. Antimicrob. Agents Chemother.
42: 2066-2069
[Abstract][Full Text]
Draper, C. R., Edel, M. J., Dick, I. M., Randall, A. G., Martin, G. B., Prince, R. L.
(1997). Phytoestrogens Reduce Bone Loss and Bone Resorption in Oophorectomized Rats. J. Nutr.
127: 1795-1799
[Abstract][Full Text]
De Franceschi, L., Brugnara, C., Beuzard, Y.
(1997). Dietary Magnesium Supplementation Ameliorates Anemia in a Mouse Model of beta -Thalassemia. Blood
90: 1283-1290
[Abstract][Full Text]
GROSSET, J., LOUNIS, N., TRUFFOT-PERNOT, C., O'BRIEN, R. J., RAVIGLIONE, M. C., JI, B.
(1997). Once-weekly Rifapentine-containing Regimens for Treatment of Tuberculosis in Mice. Am. J. Respir. Crit. Care Med.
157: 1436-1440
[Abstract][Full Text]
Haugan, K., Shalmi, M., Petersen, J. S., Marcussen, N., Spannow, J., Christensen, S.
(1997). Effects of Renal Papillary-Medullary Lesion on the Antihypertensive Effect of Furosemide and Development of Salt-Sensitive Hypertension in Dahl-S Rats. J. Pharmacol. Exp. Ther.
280: 1415-1422
[Abstract][Full Text]
Begg, C., Cho, M., Eastwood, S., Horton, R., Moher, D., Olkin, I., Pitkin, R., Rennie, D., Schulz, K. F., Simel, D., Stroup, D. F.
(1996). Improving the Quality of Reporting of Randomized Controlled Trials: The CONSORT Statement. JAMA
276: 637-639
[Abstract]
Gabbitas, B., Pash, J. M., Delany, A. M., Canalis, E.
(1996). Cortisol Inhibits the Synthesis of Insulin-like Growth Factor-binding Protein-5 in Bone Cell Cultures by Transcriptional Mechanisms. J. Biol. Chem.
271: 9033-9038
[Abstract][Full Text]
Marinho, N. V.S., Keogh, B. E., Costa, D. C., Lammerstma, A. A., Ell, P. J., Camici, P. G.
(1996). Pathophysiology of Chronic Left Ventricular Dysfunction : New Insights From the Measurement of Absolute Myocardial Blood Flow and Glucose Utilization. Circulation
93: 737-744
[Abstract][Full Text]
Delany, A. M., Jeffrey, J. J., Rydziel, S., Canalis, E.
(1995). Cortisol Increases Interstitial Collagenase Expression in Osteoblasts by Post-transcriptional Mechanisms. J. Biol. Chem.
270: 26607-26612
[Abstract][Full Text]
Ghaleh, B., Bea, M.-L., Dubois-Rande, J.-L., Giudicelli, J.-F., Hittinger, L., Berdeaux, A.
(1995). Endothelial Modulation of ß-Adrenergic Dilation of Large Coronary Arteries in Conscious Dogs. Circulation
92: 2627-2635
[Abstract][Full Text]
Uren, N. G., Crake, T., Lefroy, D. C., de Silva, R., Davies, G. J., Maseri, A.
(1994). Reduced Coronary Vasodilator Function in Infarcted and Normal Myocardium after Myocardial Infarction. NEJM
331: 222-227
[Abstract][Full Text]
Uren, N. G., Melin, J. A., De Bruyne, B., Wijns, W., Baudhuin, T., Camici, P. G.
(1994). Relation between Myocardial Blood Flow and the Severity of Coronary-Artery Stenosis. NEJM
330: 1782-1788
[Abstract][Full Text]
Perko, M. J., Olsen, P. S., Schroeder, T. V., Sorensen, S., Lorentzen, J. E.
(1993). Abdominal Aortic Aneurysm: Age as a Risk Factor Influencing Postoperative Survival. VASC ENDOVASCULAR SURG
27: 176-182
[Abstract]
Reynolds, E.H., Heller, A.J., Chadwick, D., Johnson, T., Hernandez-Vidal, A., Monfort, J.-C., Mattson, R. H., Collins, J. F., Cramer, J. A.
(1993). Valproate versus Carbamazepine for Seizures. NEJM
328: 207-209
[Full Text]
Markowitz, J. A., Hawkins, B. S., Diener-West, M., Schachat, A. P.
(1992). A Review of Mortality From Choroidal Melanoma: I. Quality of Published Reports, 1966 Through 1988. Arch Ophthalmol
110: 239-244
[Abstract]
Twomey, P. L.
(1991). Invented Review: Getting Started in Clinical Nutrition Research. Nutr Clin Pract
6: 175-183
[Abstract]
Meier, F. A., Centor, R. M., Graham, L. Jr, Dalton, H. P.
(1990). Clinical and Microbiological Evidence for Endemic Pharyngitis Among Adults Due to Group C Streptococci. Arch Intern Med
150: 825-829
[Abstract]
Masdeu, J. C., Wolfson, L., Lantos, G., Tobin, J. N., Grober, E., Whipple, R., Amerman, P.
(1989). Brain White-Matter Changes in the Elderly Prone to Falling. Arch Neurol
46: 1292-1296
[Abstract]
Durham, S. K., Brouwer, A.
(1989). 3,4,3',4'-Tetrachlorobiphenyl-Induced Effects in the Rat Liver. I. Serum and Hepatic Retinoid Reduction and Morphologic Changes. Toxicol Pathol
17: 536-544
[Abstract]
Sharp, K. W., Ross, C. B., Tillman, V. N., Dunn, J. F.
(1989). Common Bile Duct Healing: Do Different Absorbable Sutures Affect Stricture Formation and Tensile Strength?. Arch Surg
124: 408-414
[Abstract]
Baxter, L. R. Jr, Schwartz, J. M., Phelps, M. E., Mazziotta, J. C., Guze, B. H., Selin, C. E., Gerner, R. H., Sumida, R. M.
(1989). Reduction of Prefrontal Cortex Glucose Metabolism Common to Three Types of Depression. Arch Gen Psychiatry
46: 243-250
[Abstract]
Gwirtsman, H. E., Kaye, W. H., George, D. T., Jimerson, D. C., Ebert, M. H., Gold, P. W.
(1989). Central and Peripheral ACTH and Cortisol Levels in Anorexia Nervosa and Bulimia. Arch Gen Psychiatry
46: 61-69
[Abstract]
Ibarra-Perez, C., Lau-Cortes, E., Colmenero-Zubiate, S., Arevila-Ceballos, N., Humberto Fong, J., Sanchez-Martinez, R., Dominguez, M. V., Elizalde-Gonzalez, J.
(1988). Prevalence and Prevention of Deep Venous Thrombosis of the Lower Extremities in High-Risk Pulmonary Patients. ANGIOLOGY
39: 505-513
[Abstract]
Szechtman, H., Nahmias, C., Garnett, E. S., Firnau, G., Brown, G. M., Kaplan, R. D., Cleghorn, J. M.
(1988). Effect of Neuroleptics on Altered Cerebral Glucose Metabolism in Schizophrenia. Arch Gen Psychiatry
45: 523-532
[Abstract]
Chan, P., Vincent, J. W., Wangemann, R. T.
(1987). Accelerated Healing of Carbon Dioxide Laser Burns in Rats Treated With Composite Polyurethane Dressings. Arch Dermatol
123: 1042-1045
[Abstract]
Bauer, J. H., Reams, G. P., Lal, S. M.
(1987). Renal Protective Effect of Strict Blood Pressure Control With Enalapril Therapy. Arch Intern Med
147: 1397-1400
[Abstract]
Fuh, M. M-T., Shieh, S-M., Wu, D-A., Chen, Y-D. I., Reaven, G. M.
(1987). Abnormalities of Carbohydrate and Lipid Metabolism in Patients With Hypertension. Arch Intern Med
147: 1035-1038
[Abstract]
Browner, W. S., Newman, T. B.
(1987). Are All Significant P Values Created Equal? The Analogy Between Diagnostic Tests and Clinical Research. JAMA
257: 2459-2463
[Abstract]
Moley, J.F., Aamodt, R., Rumble, W., Kaye, W., Norton, J.A.
(1987). Body Cell Mass in Cancer-Bearing and Anorexic Patients. JPEN J Parenter Enteral Nutr
11: 219-222
[Abstract]
Baxter, L. R. Jr, Phelps, M. E., Mazziotta, J. C., Guze, B. H., Schwartz, J. M., Selin, C. E.
(1987). Local Cerebral Glucose Metabolic Rates in Obsessive-Compulsive Disorder: A Comparison With Rates in Unipolar Depression and in Normal Controls. Arch Gen Psychiatry
44: 211-218
[Abstract]
Lad, T. E., Mishoulam, H. M., Shevrin, D. H., Kukla, L. J., Abramson, E. C., Kukreja, S. C.
(1987). Treatment of Cancer-Associated Hypercalcemia With Cisplatin. Arch Intern Med
147: 329-332
[Abstract]
Solomkin, J. S., Dellinger, E. P., Christou, N. V., Mason, A. D. Jr
(1987). Design and Conduct of Antibiotic Trials: A Report of the Scientific Studies Committee of the Surgical Infection Society. Arch Surg
122: 158-164
[Abstract]
Stern, R. S.
(1986). Record Linkage: A Powerful Tool for Epidemiologic Analysis. Arch Dermatol
122: 1383-1384
[Abstract]
Unger, A., Goetzman, B. W., Chan, C., Lyons, A. B. III, Miller, M. F.
(1986). Nutritional Practices and Outcome of Extremely Premature Infants. Arch Pediatr Adolesc Med
140: 1027-1033
[Abstract]
Diamond, T. W., Botha, J. R., Wing, J., Meyers, A. M., Kalk, W. J.
(1986). Parathyroid Hypertension: A Reversible Disorder. Arch Intern Med
146: 1709-1712
[Abstract]
Spizz, G., Blackshear, P. J.
(2001). Overexpression of the Myristoylated Alanine-rich C-kinase Substrate Inhibits Cell Adhesion to Extracellular Matrix Components. J. Biol. Chem.
276: 32264-32273
[Abstract][Full Text]
Scherzer, P., Popovtzer, M. M.
(2002). Segmental localization of mRNAs encoding Na+-K+-ATPase alpha 1- and beta 1-subunits in diabetic rat kidneys using RT-PCR. Am. J. Physiol. Renal Physiol.
282: F492-F500
[Abstract][Full Text]
Production by Tristetraprolin. Science
281: 1001-1005
Previous
