+/* One-pass moments. Use only if two passes are impractical. */
+struct moments1 *moments1_create (enum moment max_moment);
+void moments1_clear (struct moments1 *);
+void moments1_add (struct moments1 *, double value, double weight);
+void moments1_calculate (const struct moments1 *,
+ double *weight,
+ double *mean, double *variance,
+ double *skewness, double *kurtosis);
+void moments1_destroy (struct moments1 *);
+
+/* Standard errors. */
+double calc_semean (double stddev, double weight);