TY - JOUR
T1 - The chi-square test
T2 - Its use in rehabilitation research
AU - Ottenbacher, Kenneth J.
N1 - Funding Information:
From the State University of New York at Buffalo. Supported in part from a grant sponsored by the National Institute on Disability and Rehabilitation Research (NIDRR), US Department of Education (grant HI 33B30041). Submitted for publication November 7, 1994. Accepted in revised form February 14, 1995. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Kenneth Ottenbacher, PhD, OTR, SUNY at Buffalo, 232 Parker Hall, Main Street Campus, Buffalo, NY 14214. © 1995 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/95/7607-329753.00/0
PY - 1995/7
Y1 - 1995/7
N2 - Objective: This report examines the impact of collecting and analyzing sequential data from the same sample using the chi-square test. Researchers in rehabilitation frequently analyze categorical data collected repeatedly from the same sample. Design: Simulations were conducted using the chi-square test to analyze data with correlations between pretest and posttest ranging from .20 to .80. The simulations were analyzed using the standard chi-square based on a 2 × 2 contingency table. Results: An incidence of type 1 errors of approximately .30 for an expected alpha of .05 was found when the correlation (serial dependence) between pretest and posttest was high (phi = .80). For simulations using an α = .01, the type 1 error rate was .18 for data with substantial correlation (phi = .80). Conclusion: Rehabilitation researchers who use the chi-square test with data collected repeatedly from the same sample risk committing a type 1 error and misinterpreting their results. Alternatives to the standard chi-square test, such as McNemar's test, should be considered when correlated data are analyzed using a 2 × 2 contingency table.
AB - Objective: This report examines the impact of collecting and analyzing sequential data from the same sample using the chi-square test. Researchers in rehabilitation frequently analyze categorical data collected repeatedly from the same sample. Design: Simulations were conducted using the chi-square test to analyze data with correlations between pretest and posttest ranging from .20 to .80. The simulations were analyzed using the standard chi-square based on a 2 × 2 contingency table. Results: An incidence of type 1 errors of approximately .30 for an expected alpha of .05 was found when the correlation (serial dependence) between pretest and posttest was high (phi = .80). For simulations using an α = .01, the type 1 error rate was .18 for data with substantial correlation (phi = .80). Conclusion: Rehabilitation researchers who use the chi-square test with data collected repeatedly from the same sample risk committing a type 1 error and misinterpreting their results. Alternatives to the standard chi-square test, such as McNemar's test, should be considered when correlated data are analyzed using a 2 × 2 contingency table.
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U2 - 10.1016/S0003-9993(95)80639-3
DO - 10.1016/S0003-9993(95)80639-3
M3 - Article
C2 - 7605189
AN - SCOPUS:0029049722
SN - 0003-9993
VL - 76
SP - 678
EP - 681
JO - Archives of Physical Medicine and Rehabilitation
JF - Archives of Physical Medicine and Rehabilitation
IS - 7
ER -