Consider a sample with a mean of  and a standard deviation of . What are the z-scores for the following data values: , , , , and ? Round your answers to 2 decimal places and enter negative values as negative numbers, if necessary. If your answer is zero, enter “0”.

Data Value	-score
520
655
510
450
285

Suppose the data have a bell-shaped distribution with a mean of  and a standard deviation of . Use the empirical rule to determine the percentage of data within of the following range:

 

22 to 38	- Select your answer -Approximately 68%Approximately 75%Approximately 89%Approximately 94%Approximately 95%Almost allItem 1
18 to 42	- Select your answer -Approximately 68%Approximately 75%Approximately 89%Approximately 94%Approximately 95%Almost allItem 2
26 to 34	- Select your answer -Approximately 68%Approximately 75%Approximately 89%Approximately 94%Approximately 95%Almost allItem 3

The Energy Information Administration reported that the mean retail price per gallon of regular grade gasoline was . Suppose that the standard deviation was  and that the retail price per gallon has a bell-shaped distribution.

NOTE: Please use empirical rule approximations for this problem.

a. What percentage of regular grade gasoline sold between $3.30 and $3.70 per gallon (to 1 decimal)?

 

b. What percentage of regular grade gasoline sold between $3.30 and $3.60 per gallon (to 1 decimal)?

 

c. What percentage of regular grade gasoline sold for less than $3.70 per gallon (to 1 decimal)?