In a survey of sleeping habits, 8400 national adults were selected randomly and contacted by telephone. Respondents were asked, "Typically, how many times per week do you sleep less than 6 hours during the night

C) 1.8 is a statistic and represents an estimate of the unknown value of a parameter of  interest.

Step-by-step explanation:

The complete question is: In a survey of sleeping habits, 8400 national adults were selected randomly and contacted by telephone.

Respondents were asked: “Typically, how many times per week do you sleep less than 6 hours during  the night?” On average, those surveyed reported an average of 1.8 nights per week in which they got  less than 6 hours of sleep. Which of the following is true with respect to this scenario?

A) 8400 is the size of the population being studied.

B) 1.8 is a parameter and represents an estimate of the unknown value of a statistic of  interest.

C) 1.8 is a statistic and represents an estimate of the unknown value of a parameter of  interest.

D) None of the above

We are given that in a survey of sleeping habits, 8400 national adults were selected randomly and contacted by telephone.  

On average, those surveyed reported an average of 1.8 nights per week in which they got  less than 6 hours of sleep.

In the question 8400 is the sample size (n) as it is taken from the population to conduct a survey.

So, the statement is not true that 8400 is the size of the population being studied. It is the size of the sample being tested.

Also, the sample mean = 1.8 nights per week, it is sample or statistic value because it is calculated using sample size value and it is an estimate or representation of the population unknown parameter.

So, the correct statement is that 1.8 is a statistic and represents an estimate of the unknown value of a parameter of  interest.