Answer:
The margin of error for the 95% confidence interval for the mean score of all such subjects is of 8.45.
Step-by-step explanation:
We have the standard deviation for the sample, which means that the t-distribution is used to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 27 - 1 = 26
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 26 degrees of freedom(y-axis) and a confidence level of  . So we have T = 2.0518
. So we have T = 2.0518
The margin of error is:

In which s is the standard deviation of the sample and n is the size of the sample.
In this question:
 . So
. So


The margin of error for the 95% confidence interval for the mean score of all such subjects is of 8.45.
 
        
             
        
        
        
Answer:
D. 0.925x + 0.88y = 0.91(x + y)  
Step-by-step explanation:
The important point to remember is that the total mass of pure silver is the same on each side of the equation.
0.925x = mass of pure silver in first alloy
0.88  y = mass of pure silver in second alloy
The final alloy has a mass of (x + y) g and is 91 % pure silver, so
0.925x + 0.88y = 0.91(x + y)
 
        
                    
             
        
        
        
Answer:
A, yes.
Step-by-step explanation:
63:60, 21:20:
The difference between 60 and 20 is *3. If you do that to 21, you get 63. So a , yes.