F-statistic and Significance


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F-statistic is a value resulting from a standard statistical test used in ANOVA and regression analysis to determine if the variances between the means of two populations are significantly different. For practical purposes, it is important to know that this value determines the P-value, but the F-statistic number will not actually be used in the interpretation here.

Significance, or P-value, is the probability that an effect at least as extreme as the current observation has occurred by chance. Therefore, in these particular examples the chance that the prevalence of low waz dropped from 38% to 26% in for better roofing groups and from 40% to 16% in groups with higher education is unlikely to have occurred by chance. For the roofing example, P or Sig=0.031, 97 of every 100 times this difference would not occur by chance alone. For the education example, P or Sig= 0.000, there greater than 99.9% certainty that the difference did not occur by chance. In medical research, if the P-value is less than or equal to 0.05, meaning that there is no more than a 5%, or a 1 in 20, probability of observing a result as extreme as that observed solely due to chance, then the association between the exposure and disease is considered statistically significant.

Hennekens, C. H., Epidemiology in Medicine. Boston: Little, Brown and Co., 1987.