Answer:
 
 
Now we just take square root on both sides of the interval and we got:
 
And the best option would be:
A.  2.2 < σ < 2.8
Step-by-step explanation:
Information provided
 represent the sample mean
 represent the sample mean
 population mean
 population mean  
s=2.4 represent the sample standard deviation
n=83 represent the sample size  
Confidence interval
The confidence interval for the population variance is given by the following formula:
 
The degrees of freedom are given by:
 
The Confidence is given by 0.90 or 90%, the value of  and
 and  , the critical values for this case are:
, the critical values for this case are:
 
 
And replacing into the formula for the interval we got:
 
 
Now we just take square root on both sides of the interval and we got:
 
And the best option would be:
A.  2.2 < σ < 2.8
 
        
             
        
        
        
Since most of these are mixed number you have to convert them into improper fractions. 
For an example 2 3/4 x 1/2
First you would have the convert 2 3/4 
You would add 2 to 3 then multiply 2 to 4 
So it would be (2x4) + 3 
You keep the denominator of the originally fraction so it would be 11/4
Then to finish you would multiply straight across so
11x1= 11
4x2=8
11/8 
1 3/8 
Hope this helps!!
        
             
        
        
        
Answer:
Unit 4- Expressions and Equations: In this unit, students build on their knowledge from unit 2, where they extended the laws of exponents to rational exponents. Students apply this new understanding of number and strengthen their ability to see structure in and create quadratic and exponential expressions.
 
        
             
        
        
        
Answer:
95%
Step-by-step explanation:
The empirical rule states that if data follows normal distribution then the percentage of observations falls within one, two and three standard deviation around the mean are
i) 68% falls within one standard deviation
ii) 95% falls within two standard deviation 
iii) 99.7% falls within three standard deviation.
Hence 95% of the observations will fall within two standard deviations around the mean if the data follows normal distribution.