Question

the variance is zero, if all abservations are

Answer 1

If the variance of a data set is zero, then all the observations in this data set must be zero is false. If variance is equal to 0, then each observed value is equal to the mean of the data set.

Answer 2

Explanation:

Greying of hair is caused when cells at the hair base (melanocytes) stop producing the pigment which is responsible for giving our hair its colour. To continue making the colour-producing pigment, the cells need Vitamin B12. In some cases, premature greying occurs if there's a deficiency of Vitamin B12.