Sample Variance = result from the sample data
Unbiased Variance = result considering the population

Formula
Sample Variance

Formula
Unbiased Variance

unbiased_variance<−var(test_result)
sample_variance<−unbiased_variance*(n−1)/n

Standard deviation from unbiased variance = sd(test_result)
Standard deviation from sample variance = sqrt(sd(test_result)^2*(data−1)/n)
sqrt(sample_variance)