Observer bias

Biased treatment outcome assessment can result if people receiving or providing care, or others assessing treatment outcomes, know which participants have received which treatments. It is sometimes possible to conceal which treatments have been received by using placebos and in other ways. See also Double Dummy.

156 RECORDS
33 ARTICLES

The need to address treatment uncertainties

Principles of Testing

Treatment comparisons are essential

Treatment comparisons must be fair

Biases

Double dummy

The play of chance

Bringing it all together for the benefit of patients and the public

James Lind LibraryIllustrating the development of fair tests of treatments in health care

Observer bias

SORT date ▲ author

156 RECORDS

33 ARTICLES

Bacon F (1645) Franc Baconis de Verulamio / Summi Angliae Cancellarii /Novum organum scientiarum. Lugd. Bat: apud Adrianum Wiingaerde, et Franciscum Moiardum. Aphorism XLVI (pages 45-46).

Commission Royale. Bailly A (1784) Rapport des commissaires chargés par le Roi, de l'examen du magnétisme animale [Report of the Comissioners required by the King to examine animal magnetism]. Imprimé par ordre du Roi. Paris: A Paris, de L'Imprimerie Royale.

Haygarth J (1800) Of the imagination, as a cause and as a cure of disorders of the body: exemplified by fictitious tractors, and epidemical convulsions. Bath: R. Crutwell.

Löhner G, on behalf of a Society of truth-loving men (1835) Die Homoöopathischen Kochsalzversuche zu Nürnberg [The homeopathic salt trials in Nurnberg]. Nürnberg in März.

Storke EF, Martin R, Rosenkrans EM, Ford J, Schloemilch A, McDermott GC, Carlson OW (1880) Final report of the Milwaukee test of the thirtieth dilution. Homoeopathic Times 7:12/280-1.

Hartridge G (1886) Tobacco amblyopia. BMJ 1:200.

Stuart W (1889) A remarkable case of morphine addiction. BMJ 1:1051-52.

Behring EA, Boer NN, Kossel H (1893) Zur Behandlung diphtheriekranker Menschen mit Diphtherieheilserum [On the treatment of diphtheria patients with curative diphtheria serum]. Deutsche Medicinische Wochenschrift 17:389-39.

Pregl F (1896) Zwei weitere ergographische Versuchsreihen über die Wirkung orchistischen Extraktes [Two further ergographic experimental series on the effects of testicular extracts]. Archiv für die gesamte Physiologie 62:379-399.

Vorderman AG (1897) Onderzoek naar het verband tusschen den aard der rijstvoeding in de gevangenissen op Java en Madoera en het voorkomen van beri-beri onder de geïnterneerden. Batavia: Jav. Boekh. & Drukkerij.

Cotton FJ (1899) The Present Status of the Antistreptococcic Serum. New England Journal of Medicine 140:105-109. DOI: 10.1056/NEJM189902021400501

Rivers WHR (1908) The influence of alcohol and other drugs on fatigue. London: Edward Arnold.

Anonymous (1908) Alcohol in the treatment of pneumonia and enteric fever. Lancet 157:442.

Freeman J (1910) Vaccine therapy. Proceedings of the Royal Society of Medicine 3:97-101.

Jansen H (1910) Behandling med Radiumemanation særlig ved gigtiske Lidelser [Treatment with radium emanation especially with rheumatic diseases]. Ugeskrift for Læger 72:1333-48.

Hollingworth HL (1911) The influence of caffeine on mental and motor efficiency. Archives of Psychology/Columbia Contributions to Philosophy and Psychology 20:iii-v

Solis-Cohen M, Strickler A (1911) The effect produced by some therapeutic measures on the different forms of leucocytes in pulmonary tuberculosis. New England Journal of Medicine 165:563-568.

Hewlett AW (1913) Clinical effects of “natural” and “synthetic” sodium salicylate. JAMA 61:319-321.

Council on Pharmacy and Chemistry (1913) Sinkina. JAMA 61:1056-1058.

Wesselhoeft W (1915) Hospital Efficiency from the Standpoint of Hospital Trustees. The New England Journal of Medicine 172:778. 10.1056/NEJM191505271722104

Bastedo WA (1915) Clinical Experience with Liquid Paraffin (Liquid Petrolatum): A Comparative Investigation Made Under the Auspices of the Council on Pharmacy and Chemistry. JAMA 64: 808-809.

Plass ED (1916) Post partum care of perineum. Bulletin of Johns Hopkins Hospital 27:107-109.

Goadby K (1916) An inquiry into the natural history of septic wounds. Lancet 188: 89-95.

Von Sholly AI, Blum J, Smith L (1917) The therapeutic value of pertussis vaccine in whooping cough. JAMA 68:1451-1456.

Sollmann T (1917) The crucial test of therapeutic evidence. JAMA 69:198-199.

Leake JP (1917) Bacterial vaccine therapy. JAMA 69:631-632.

Bingel A (1918) Über Behandlung der Diphtherie mit gewöhnlichem Pferdeserum [On the treatment of diphtheria with normal horse serum]. Deutsches Archiv für Klinische Medizin 125:284-332.

Freeman J (1929) Discussion on the action and use of ephedrine. Proceeding of Royal Society of Medicine 22:1369.

Amberson JB, McMahon BT, Pinner M (1931) A clinical trial of sanocrysin in pulmonary tuberculosis. American Review of Tuberculosis 24:401-435.

Martini P (1932) Methodenlehre der Therapeutischen Untersuchung [Methodological principles for therapeutic investigations]. Berlin: Springer.

Diehl HS (1933) Medicinal treatment of the common cold. JAMA 101:2042-2049.

Evans W, Hoyle C (1933) The comparative value of drugs used in the continuous treatment of angina pectoris. Quarterly Journal of Medicine 7:311-338.

Evans W, Hoyle C (1934) The prevention and treatment of individual attacks of angina pectoris (angina of effort). Quarterly Journal of Medicine 3:105-135.

Hediger E, Gold H (1935) USP ether from large drums and ether from small cans labeled ‘For Anesthesia’. JAMA 104:2244-2448.

Corrigan JG, Strauss MB (1936) The prevention of hypochromic anaemia in pregnancy. JAMA 106:1088-1090.

Hesseltine HC (1937) Evaluation by controlled series of vaginal trichomoniasis therapies. JAMA 109:768-71.

Cookson H, Facey RV (1937) Value of a specific serum in the treatment of typhoid fever. BMJ 1:1009-1012.

Pratt JP, Thomas WL (1937) The endocrine treatment of menopausal phenomena. JAMA 109:1875-1880.

Wilbur DL, MacLean AR, Allen EV (1937) Clinical observations on the effect of Benzedrine sulphate. JAMA 109:549-54.

Gold H, Kwit NT, Otto H (1937) The xanthines (theobromine and aminophyllin) in the treatment of cardiac pain. JAMA 108;2173-2179.

Field JW, Niven JC, Hodgkin EP (1937) The prevention of malaria in the field by the use of quinine and atebrine. Bulletin of the Health Organisation of the League of Nations 6:236-290.

Bastianelli G, Mosna E, Canalis A (1937) Prevention and treatment of malaria by synthetic drugs. Bulletin of the Health Organisation of the League of Nations 6:822-891.

Bahnsen P, Jacobsen E, Thesleff H (1938) Studien über die Wirkung von beta-phenyl-isopropylaminsulfdat (Mecodrin) auf normale Menschen. [Studies on the effect of beta-phenyl-isopropylaminsulfdat (Mecodrin) on normal volunteers]. Klinische Wochenschrift 17:1074-1078.

Diehl HS, Baker AB, Cowan DW (1938) Cold vaccines: an evaluation based on a controlled study. Journal of American Medical Association 111:1168-1173.

Murless BC (1939) Effect of follicular hormone on menopausal flushes. Lancet 233:1205-1206.

Dub LA, Lurie LA (1939) Use of benzedrine in the depressed phase of the psychotic state. Ohio State Medical Journal 35:39-45.

Evans W, Loughman O (1939) The drug treatment of hyperpiesia. British Heart Journal 1:199-228.

Master AM, Jaffe HL, Dack S (1939) The drug treatment of angina pectoris due to coronary artery disease. American Journal of Medical Science 197:774-782.

Sidell N, Abrams MI (1940) Treatment of chronic arthritis. JAMA 144:1740-1742.

Alstead S (1941) Action of Bismuth Carbonate in gastric disease. Lancet 238: 420-423.

Bell JA (1941) Pertussis prophylaxis with two doses of alum-precipitated vaccine. Public Health Reports 56:1535-1546.

Miller M (1941) Benzedrine sulphate in the treatment of nicotinism. Medical Record 2:590-593.

Stuart-Harris CH, Francis AE, Stansfeld JM (1943) Patulin in the common cold. Lancet 2:684.

Payne WW (1943) Vitamin C in school-children. Lancet 41:819-820.

Sigler LH, Tulgan J (1943) Treatment of angina pectoris by testosterone propionate. New York State Journal of Medicine 43:1424-1428.

British Homoeopathic Society (1943) Report on mustard gas experiments (Glasgow and London). British Homoeopathic Journal 33:1-12.

Harper AA, MacKay IFS, Raper HS, Camm GL (1943) Vitamins and physical fitness. BMJ 1:243–245.

Hopkins WA (1943) Patulin in the common cold. IV: Biological properties: extended trial in the common cold. Lancet 2:630-635.

Holling HE, McArdle B, Trotter WR (1944) Prevention of seasickness by drugs. Lancet 243:127-129.

Stansfeld JM, Francis AE, Stuart-Harris CH (1944) Laboratory and clinical trials of Patulin. Lancet 2:370-372.

Fraser TN (1944) Gold treatment in rheumatoid arthritis. Annals of Rheumatic Diseases. 4:71-75.

Medical Research Council (1944) Clinical trial of patulin in the common cold. Lancet 2:373-5.

Scadding JG (1944) Comparative effects of sulphonamide drugs in mild bacillary dysentery. Lancet 1:784-786.

Anderson T (1944) Clinical studies in sulphonamide chemotherapy. MD thesis, University of Glasgow.

Hill IGW, Guest AI (1945) Prevention of sea-sickness in assault craft. BMJ 2:6–11.

MacLeod CM, Hodges RG, Heidelberger M, Bernhard WG (1945) Prevention of pneumococcal pneumonia by immunization with specific capsular polysaccharides. Journal of Experimental Medicine 82:445-465.

Colebrook D (1946) Artificial sunlight treatment in industry. MRC Industrial Health Research Board Report No. 89. London: His Majesty’s Stationery Office.

Sher N (1946) Delayed menstruation: causes and treatment. BMJ 1:347 – 349.

Jellinek EM (1946) Clinical tests on comparative effectiveness of analgesic drugs. Biometric Bulletin 2:87-91.

Bransby ER, Burn JL, Magee HE, MacKecknie DM (1946) Effect of a daily vitamin supplement on the health and development of children. BMJ 1:193-197.

Glickman I (1947) The use of penicillin lozenges in the treatment of Vincent’s infection and other acute gingival inflammations. Journal of the American Dental Association 34:406-409.

Wills L, Hill G, Bingham K, Miall M, Wrigley J (1947) Haemoglobin levels in pregnancy. The effect of the rationing scheme and routine administration of iron. British Journal of Nutrition 1:126-138.

MRC Vitamin C subcommittee (1948) Vitamin-C requirement of human adults. Experimental study of Vitamin-C deprivation in man. Lancet 251: 852-858.

Asher R (1948) A method of testing analgesics. Lancet 2:771-3.

Bell JA (1948) Pertussis immunization use of two doses of an alum-precipitated mixture of diphtheria toxoid and pertussis vaccine. JAMA 137:1276-1281.

James Lind Library
Illustrating the development of fair tests of treatments in health care

Bacon F (1645)
Franc Baconis de Verulamio / Summi Angliae Cancellarii /Novum organum scientiarum. Lugd. Bat: apud Adrianum Wiingaerde, et Franciscum Moiardum. Aphorism XLVI (pages 45-46).

Commission Royale. Bailly A (1784)
Rapport des commissaires chargés par le Roi, de l'examen du magnétisme animale [Report of the Comissioners required by the King to examine animal magnetism]. Imprimé par ordre du Roi. Paris: A Paris, de L'Imprimerie Royale.

Haygarth J (1800)
Of the imagination, as a cause and as a cure of disorders of the body: exemplified by fictitious tractors, and epidemical convulsions. Bath: R. Crutwell.

Löhner G, on behalf of a Society of truth-loving men (1835)
Die Homoöopathischen Kochsalzversuche zu Nürnberg [The homeopathic salt trials in Nurnberg]. Nürnberg in März.

Storke EF, Martin R, Rosenkrans EM, Ford J, Schloemilch A, McDermott GC, Carlson OW (1880)
Final report of the Milwaukee test of the thirtieth dilution. Homoeopathic Times 7:12/280-1.

Hartridge G (1886)
Tobacco amblyopia. BMJ 1:200.

Stuart W (1889)
A remarkable case of morphine addiction. BMJ 1:1051-52.

Behring EA, Boer NN, Kossel H (1893)
Zur Behandlung diphtheriekranker Menschen mit Diphtherieheilserum [On the treatment of diphtheria patients with curative diphtheria serum]. Deutsche Medicinische Wochenschrift 17:389-39.

Pregl F (1896)
Zwei weitere ergographische Versuchsreihen über die Wirkung orchistischen Extraktes [Two further ergographic experimental series on the effects of testicular extracts]. Archiv für die gesamte Physiologie 62:379-399.

Vorderman AG (1897)
Onderzoek naar het verband tusschen den aard der rijstvoeding in de gevangenissen op Java en Madoera en het voorkomen van beri-beri onder de geïnterneerden. Batavia: Jav. Boekh. & Drukkerij.

Cotton FJ (1899)
The Present Status of the Antistreptococcic Serum. New England Journal of Medicine 140:105-109. DOI: 10.1056/NEJM189902021400501

Rivers WHR (1908)
The influence of alcohol and other drugs on fatigue. London: Edward Arnold.

Anonymous (1908)
Alcohol in the treatment of pneumonia and enteric fever. Lancet 157:442.

Freeman J (1910)
Vaccine therapy. Proceedings of the Royal Society of Medicine 3:97-101.

Jansen H (1910)
Behandling med Radiumemanation særlig ved gigtiske Lidelser [Treatment with radium emanation especially with rheumatic diseases]. Ugeskrift for Læger 72:1333-48.

Hollingworth HL (1911)
The influence of caffeine on mental and motor efficiency. Archives of Psychology/Columbia Contributions to Philosophy and Psychology 20:iii-v

Solis-Cohen M, Strickler A (1911)
The effect produced by some therapeutic measures on the different forms of leucocytes in pulmonary tuberculosis. New England Journal of Medicine 165:563-568.

Hewlett AW (1913)
Clinical effects of “natural” and “synthetic” sodium salicylate. JAMA 61:319-321.

Council on Pharmacy and Chemistry (1913)
Sinkina. JAMA 61:1056-1058.

Wesselhoeft W (1915)
Hospital Efficiency from the Standpoint of Hospital Trustees. The New England Journal of Medicine 172:778. 10.1056/NEJM191505271722104

Bastedo WA (1915)
Clinical Experience with Liquid Paraffin (Liquid Petrolatum): A Comparative Investigation Made Under the Auspices of the Council on Pharmacy and Chemistry. JAMA 64: 808-809.

Plass ED (1916)
Post partum care of perineum. Bulletin of Johns Hopkins Hospital 27:107-109.

Goadby K (1916)
An inquiry into the natural history of septic wounds. Lancet 188: 89-95.

Von Sholly AI, Blum J, Smith L (1917)
The therapeutic value of pertussis vaccine in whooping cough. JAMA 68:1451-1456.

Sollmann T (1917)
The crucial test of therapeutic evidence. JAMA 69:198-199.

Leake JP (1917)
Bacterial vaccine therapy. JAMA 69:631-632.

Bingel A (1918)
Über Behandlung der Diphtherie mit gewöhnlichem Pferdeserum [On the treatment of diphtheria with normal horse serum]. Deutsches Archiv für Klinische Medizin 125:284-332.

Freeman J (1929)
Discussion on the action and use of ephedrine. Proceeding of Royal Society of Medicine 22:1369.

Amberson JB, McMahon BT, Pinner M (1931)
A clinical trial of sanocrysin in pulmonary tuberculosis. American Review of Tuberculosis 24:401-435.

Martini P (1932)
Methodenlehre der Therapeutischen Untersuchung [Methodological principles for therapeutic investigations]. Berlin: Springer.

Diehl HS (1933)
Medicinal treatment of the common cold. JAMA 101:2042-2049.

Evans W, Hoyle C (1933)
The comparative value of drugs used in the continuous treatment of angina pectoris. Quarterly Journal of Medicine 7:311-338.

Evans W, Hoyle C (1934)
The prevention and treatment of individual attacks of angina pectoris (angina of effort). Quarterly Journal of Medicine 3:105-135.

Hediger E, Gold H (1935)
USP ether from large drums and ether from small cans labeled ‘For Anesthesia’. JAMA 104:2244-2448.

Corrigan JG, Strauss MB (1936)
The prevention of hypochromic anaemia in pregnancy. JAMA 106:1088-1090.

Hesseltine HC (1937)
Evaluation by controlled series of vaginal trichomoniasis therapies. JAMA 109:768-71.

Cookson H, Facey RV (1937)
Value of a specific serum in the treatment of typhoid fever. BMJ 1:1009-1012.

Pratt JP, Thomas WL (1937)
The endocrine treatment of menopausal phenomena. JAMA 109:1875-1880.

Wilbur DL, MacLean AR, Allen EV (1937)
Clinical observations on the effect of Benzedrine sulphate. JAMA 109:549-54.

Gold H, Kwit NT, Otto H (1937)
The xanthines (theobromine and aminophyllin) in the treatment of cardiac pain. JAMA 108;2173-2179.

Field JW, Niven JC, Hodgkin EP (1937)
The prevention of malaria in the field by the use of quinine and atebrine. Bulletin of the Health Organisation of the League of Nations 6:236-290.

Bastianelli G, Mosna E, Canalis A (1937)
Prevention and treatment of malaria by synthetic drugs. Bulletin of the Health Organisation of the League of Nations 6:822-891.

Bahnsen P, Jacobsen E, Thesleff H (1938)
Studien über die Wirkung von beta-phenyl-isopropylaminsulfdat (Mecodrin) auf normale Menschen. [Studies on the effect of beta-phenyl-isopropylaminsulfdat (Mecodrin) on normal volunteers]. Klinische Wochenschrift 17:1074-1078.

Diehl HS, Baker AB, Cowan DW (1938)
Cold vaccines: an evaluation based on a controlled study. Journal of American Medical Association 111:1168-1173.

Murless BC (1939)
Effect of follicular hormone on menopausal flushes. Lancet 233:1205-1206.

Dub LA, Lurie LA (1939)
Use of benzedrine in the depressed phase of the psychotic state. Ohio State Medical Journal 35:39-45.

Evans W, Loughman O (1939)
The drug treatment of hyperpiesia. British Heart Journal 1:199-228.

Master AM, Jaffe HL, Dack S (1939)
The drug treatment of angina pectoris due to coronary artery disease. American Journal of Medical Science 197:774-782.

Sidell N, Abrams MI (1940)
Treatment of chronic arthritis. JAMA 144:1740-1742.

Alstead S (1941)
Action of Bismuth Carbonate in gastric disease. Lancet 238: 420-423.

Bell JA (1941)
Pertussis prophylaxis with two doses of alum-precipitated vaccine. Public Health Reports 56:1535-1546.

Miller M (1941)
Benzedrine sulphate in the treatment of nicotinism. Medical Record 2:590-593.

Stuart-Harris CH, Francis AE, Stansfeld JM (1943)
Patulin in the common cold. Lancet 2:684.

Payne WW (1943)
Vitamin C in school-children. Lancet 41:819-820.

Sigler LH, Tulgan J (1943)
Treatment of angina pectoris by testosterone propionate. New York State Journal of Medicine 43:1424-1428.

British Homoeopathic Society (1943)
Report on mustard gas experiments (Glasgow and London). British Homoeopathic Journal 33:1-12.

Harper AA, MacKay IFS, Raper HS, Camm GL (1943)
Vitamins and physical fitness. BMJ 1:243–245.

Hopkins WA (1943)
Patulin in the common cold. IV: Biological properties: extended trial in the common cold. Lancet 2:630-635.

Holling HE, McArdle B, Trotter WR (1944)
Prevention of seasickness by drugs. Lancet 243:127-129.

Stansfeld JM, Francis AE, Stuart-Harris CH (1944)
Laboratory and clinical trials of Patulin. Lancet 2:370-372.

Fraser TN (1944)
Gold treatment in rheumatoid arthritis. Annals of Rheumatic Diseases. 4:71-75.

Medical Research Council (1944)
Clinical trial of patulin in the common cold. Lancet 2:373-5.

Scadding JG (1944)
Comparative effects of sulphonamide drugs in mild bacillary dysentery. Lancet 1:784-786.

Anderson T (1944)
Clinical studies in sulphonamide chemotherapy. MD thesis, University of Glasgow.

Hill IGW, Guest AI (1945)
Prevention of sea-sickness in assault craft. BMJ 2:6–11.

MacLeod CM, Hodges RG, Heidelberger M, Bernhard WG (1945)
Prevention of pneumococcal pneumonia by immunization with specific capsular polysaccharides. Journal of Experimental Medicine 82:445-465.

Colebrook D (1946)
Artificial sunlight treatment in industry. MRC Industrial Health Research Board Report No. 89. London: His Majesty’s Stationery Office.

Sher N (1946)
Delayed menstruation: causes and treatment. BMJ 1:347 – 349.

Jellinek EM (1946)
Clinical tests on comparative effectiveness of analgesic drugs. Biometric Bulletin 2:87-91.

Bransby ER, Burn JL, Magee HE, MacKecknie DM (1946)
Effect of a daily vitamin supplement on the health and development of children. BMJ 1:193-197.

Glickman I (1947)
The use of penicillin lozenges in the treatment of Vincent’s infection and other acute gingival inflammations. Journal of the American Dental Association 34:406-409.

Wills L, Hill G, Bingham K, Miall M, Wrigley J (1947)
Haemoglobin levels in pregnancy. The effect of the rationing scheme and routine administration of iron. British Journal of Nutrition 1:126-138.

MRC Vitamin C subcommittee (1948)
Vitamin-C requirement of human adults. Experimental study of Vitamin-C deprivation in man. Lancet 251: 852-858.

Asher R (1948)
A method of testing analgesics. Lancet 2:771-3.

Bell JA (1948)
Pertussis immunization use of two doses of an alum-precipitated mixture of diphtheria toxoid and pertussis vaccine. JAMA 137:1276-1281.

Medical Research Council (1948)
Streptomycin treatment of pulmonary tuberculosis: a Medical Research Council investigation. BMJ 2:769-782.

Makinson DH, Oleesky S, Stone RV (1948)
Vitamin E in angina pectoris. Lancet 1:102.

Bakst H, Kissin M, Leibowitz S, Rinzler S (1948)
The effects of intravenous aminophylline on the capacity of effort without pain in patients with angina of effort. American Heart Journal 36:527-534.

Elovainio E, Östling G (1948)
Observations on preoperative treatment with strophanthin. Annales Chirurgiae et Gynaecologiae Fenniae 37:23-35.