Explain why the formula for sample variance is different from the formula for population variance. Why is it inappropriate to use the formula for population variance in calculating the variance of a sample? Variance is defined as the mean squared deviation, and, for a population, is computed as the sum of squared deviations divided by N. Without some adjustment, the sample variance will be biased and will consistently underestimate the corresponding population value. Variance is defined as the mean squared deviation, and, for a population, is computed as the sum of deviations divided by N. Without some adjustment, the sample variance will be biased and will consistently underestimate the corresponding population value. Variance is defined as the mean deviation, and, for a population, is computed as the sum of deviations divided by N. Without some adjustment, the sample variance will be biased and will consistently underestimate the corresponding population value