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Answer:
A. unbiased estimator.
Step-by-step explanation:
In Statistics, an estimator is a statistical value which is used to estimate a parameter. Parameters are the determinants of the probability distribution. Therefore, to determine a normal distribution we would use the parameters, mean and variance of the population.
A function of random variables used to estimate a parameter of a distribution is an unbiased estimator.
An unbiased estimator is one in which the difference between the estimator and the population parameter grows smaller as the sample size grows larger. This simply means that, an unbiased estimator captures the true population value of the parameter on average, this is because the mean of its sampling distribution is the truth.
Also, we know that the bias of an estimator (b) that estimates a parameter (p) is given by; 
Hence, an unbiased estimator is an estimator that has an expected value that is equal to the parameter i.e the value of its bias is equal to zero (0).
<em>Generally, in statistical analysis, sample mean is an unbiased estimator of the population mean while the sample variance is an unbiased estimator of the population variance.</em>
Answer:
3
Step-by-step explanation:
If y varies directly with x, we have:

When y=12, x=4
Substituting these values into the equation
12=4k
k=12/4
k=3
The constant of proportionality is 3.
Answer:
z=12
Step-by-step explanation:
It is given that x varies jointly as y and z, it means



where, k is the constant of proportionality.
It is given that x=8 when y=4 and z=9


Divide both sides by 36.


The value of k is 2/9.

We need to find the value of z when x=16 and y=6.
Substitute x=16 and y=6 in the above equation.


Multiply both sides by 3.

Divide both sides by 4.

Therefore, the value of z is 12.
At the end of 28 years, there will be 22,083.2 dollars in the account.
Step-by-step explanation:
Step 1; First we must calculate how much interest there is in total over 28 years. The annual interest rate is 8.25% i.e. 8.25% of 6,700 dollars which equals 552.75 dollars. As the years' pass, more and more will be put into the account due to interest. After 28 years, there will be an interest of 229.6% (8.25% per year * 28 years)of the initial amount.
Step 2; We must find the money due to interest and add it with the money that was put in initially. The interest amount is 2.296 times the 6,700 dollars which was put in. The interest equals 15,383.2 dollars. With this, the initial 6,700 dollars is added which comes to a total of 22,083.2 dollars