Answer:


And for this case since the confidence interval contains the value 0 we don't have significant evidence that we have a net change in the levels 
Step-by-step explanation:
For this case we have the following info given:
 represent the sample size
 represent the sample size
 represent the sample mean
 represent the sample mean
 represent the sample deviation
 represent the sample deviation
We can calculate the confidence interval for the mean with the following formula:

The confidence level is 0.90 then the significance level would be  and the degrees of freedom are given by:
 and the degrees of freedom are given by:

And the critical value for this case would be:

And replacing we got:


And for this case since the confidence interval contains the value 0 we don't have significant evidence that we have a net change or efectiveness in the levels 
 
        
             
        
        
        
Which one?????????????????
 
        
                    
             
        
        
        
Using the normal distribution, it is found that 63.18% of the area under the curve of the standard normal distribution is between z = − 0.9 z = - 0.9.
<h3>Normal Probability Distribution</h3>
The z-score of a measure X of a normally distributed variable with mean  and standard deviation
 and standard deviation  is given by:
 is given by:

- The z-score measures how many standard deviations the measure is above or below the mean. 
- Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.
The area within 0.9 standard deviations of the mean is the <u>p-value of Z = 0.9(0.8159) subtracted by the p-value of Z = -0.9(0.1841)</u>, hence:
0.8159 - 0.1841 = 0.6318 = 63.18%.
More can be learned about the normal distribution at brainly.com/question/4079902
#SPJ1
 
        
             
        
        
        
Answer:
Reflection
Step-by-step explanation:
Because reflecting yourself in a mirror means pre image to image