The article by Philip W. Hedrick examines and compares five different measures of gametic disequilibrium (LD) currently in use, along with a new measure based on R. C. Lewontin's $D'$. The author highlights several important criteria for selecting an appropriate measure, including biological interpretation, statistical tests, mathematical relationship to evolutionary factors, and standardization for comparison across loci or populations. The measures are evaluated based on their dependence on allelic frequencies, the rate of decay of LD in infinite populations, and their distributions in samples from equilibrium populations. Key findings include: 1. **Frequency Dependence**: Most measures are highly dependent on allelic frequencies, with some measures showing negative values under maximum disequilibrium conditions. 2. **Rate of Decay**: The rate of decay of LD varies among measures, with $D^2$, $D^*$, and $Q^*$ decaying at a constant rate per generation, while $D'$ and $F'$ have more complex decay rates that depend on the initial gametic array. 3. **Distribution**: All measures have large variances, with right-skewed and platykurtic distributions, particularly for $D^2$, $D^*$, and $X(2)$. 4. **Correlation**: Measures like $D^2$, $D^*$, and $X(2)$ are highly correlated, while $F'$ and $D'$ have lower correlations. The author concludes that frequency-independent measures like $D'$ are preferable to frequency-dependent measures such as $D^2$, $D^*$, $Q^*$, $F'$, and $X(2)$, which can lead to mistaken conclusions, especially in studies inferring recombinational hot spots and the effects of population bottlenecks. The article emphasizes the importance of choosing a suitable measure to ensure confidence in conclusions based on statistical associations of alleles at different loci.The article by Philip W. Hedrick examines and compares five different measures of gametic disequilibrium (LD) currently in use, along with a new measure based on R. C. Lewontin's $D'$. The author highlights several important criteria for selecting an appropriate measure, including biological interpretation, statistical tests, mathematical relationship to evolutionary factors, and standardization for comparison across loci or populations. The measures are evaluated based on their dependence on allelic frequencies, the rate of decay of LD in infinite populations, and their distributions in samples from equilibrium populations. Key findings include: 1. **Frequency Dependence**: Most measures are highly dependent on allelic frequencies, with some measures showing negative values under maximum disequilibrium conditions. 2. **Rate of Decay**: The rate of decay of LD varies among measures, with $D^2$, $D^*$, and $Q^*$ decaying at a constant rate per generation, while $D'$ and $F'$ have more complex decay rates that depend on the initial gametic array. 3. **Distribution**: All measures have large variances, with right-skewed and platykurtic distributions, particularly for $D^2$, $D^*$, and $X(2)$. 4. **Correlation**: Measures like $D^2$, $D^*$, and $X(2)$ are highly correlated, while $F'$ and $D'$ have lower correlations. The author concludes that frequency-independent measures like $D'$ are preferable to frequency-dependent measures such as $D^2$, $D^*$, $Q^*$, $F'$, and $X(2)$, which can lead to mistaken conclusions, especially in studies inferring recombinational hot spots and the effects of population bottlenecks. The article emphasizes the importance of choosing a suitable measure to ensure confidence in conclusions based on statistical associations of alleles at different loci.