![]() ![]() The quarter-root transformation results in the most symmetric distribution, suggesting that this transformation is most appropriate for this data. In contrast, the log-transformed data are skewed to the left, suggesting that the log transformation is too strong. Here, the square-root transformed data is still slightly skewed to the right, suggesting that the square-root transformation is not strong enough. With increasingly stronger transformations of the data, the distribution shifts from being skewed to the right to being skewed to the left. The following shows histograms for the raw data (calcium), square-root transformation (S_calciu), quarter-root transformation (S_S_calc), and log transformation (L_calciu). In practice, it is generally a good idea to try all three transformations to see which appears to yield the most symmetric distribution. The square root transformation is the weakest of the above transformations, while the log transformation is the strongest. Square Root (often used with counts data).This suggests that a normalizing transformation should be considered. Note that the data appear to be skewed to the right, suggesting that calcium is not normally distributed. Here we have a histogram (produced in SAS) for daily intake of calcium. ![]()
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