So for example, if the median is equal to 0.840335, could I approximate the 25th percentile as $0.840335 / 2 = 0.4201675$?
Would this be possible if one assumes the underlying data is normally distributed?
Is dividing the median (50th percentile) by 2 an acceptable approximation of the 25th percentile?
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4Usually not. That is only half-way to zero, it is not half-way to the rest of the data. – 2017-01-11
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3The median height of American adults is probably between 5 feet and 6 feet. Would you believe that the 25th percentile of the heights of American adults is between 2.5 and 3 feet? – 2017-01-11
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2The median of $-3, -1, +1, +3$ is $0$. Half of $0$ is still zero – 2017-01-11
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0If you assume the underlying data are normally distributed, the median is the mean and the 25th percentile is the mean minus about $0.67449$ times the standard deviation. But if the mean and median are different, the data aren't normally distributed. – 2017-01-11