20. the sample mean is an unbiased estimator for the population mean. this means: (a) the sample mean always equals the population mean. (b) the average sample mean, over all possible samples, equals the population mean. (c) the sample mean is always very close to the population mean. (d) the sample mean will only vary a little from the population mean. (e) the sample mean has a normal distribution.

The answer is option b

Step-by-step explanation:

The point estimator is an unbiased estimator if its expected value is equal to the parameter that it is estimating.

In the case of the sample mean; For all possible observations of X, the expected value of the sample mean will be equal to the population mean.

option c

hope it helps

Step-by-step explanation:

in the attachment.   i didn't see your choices.   the word which means there is choices.

step-by-step explanation:

(x,y)

x tells you how much left or right you go from the origin

y tells you how much down or up you go from the origin

so for example (-3,2), you go left 3 and up twice. i denoted which of the ordered pairs is which in my graph.