ci_from_p | R Documentation |
Calculates approximate confidence interval (CI) for any given difference, based on the difference value and p value, according to Altman & Bland (2011).
ci_from_p(diff, p_value, ci = 0.95)
diff |
Difference (number) around which the CI is to be calculated. |
p_value |
The p value for CI calculation. |
ci |
Numeric; confidence level for the returned CIs ( |
CI limits as named numeric vector with two elements.
Check the Altman & Bland (2011) paper for details! (The calculation for proportions is not implemented here.)
Altman, D. G., & Bland, J. M. (2011). How to obtain the confidence interval from a P value. Bmj, 343(d2090). doi: 10.1136/bmj.d2090
# Example 1 # calculate proportion difference test proptest_stat = prop.test(x = c(49, 40), n = c(50, 50)) # calculate proportion difference my_diff = 49/50-40/50 # calculate approximate CI ci_from_p(my_diff, proptest_stat$p.value) # returned CI should be very similar to the actual CI proptest_stat$conf.int # Example 2 # generate random data v1 = stats::rnorm(190, 40, 60) v2 = stats::rnorm(170, 50, 45) # calculate t-test ttest_stat = stats::t.test(v1, v2) # calculate mean difference my_diff = mean(v1) - mean(v2) # calculate approximate CI ci_from_p(my_diff, ttest_stat$p.value) # returned CI should be similar to the actual CI ttest_stat$conf.int
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