3. A medical devices company wants to know the number of MRI machines needed per day. A previous study found a standard deviation of four hours. How many MRI machines must the company study in order to have a margin of error of 0.5 hours when calculating a 90% confidence interval

173 MRI machines

Step-by-step explanation:

Margin of error E = 0.5

Confidence interval 90% = 1-0.9 = 0.1

Standard deviation = 4 hours

Number of MRI machines needed per day n, = [(z alpha/2 * SD)/E]²

Z alpha/2 = 1.645 at alpha = 0.1

Inputting these values into n we have that

[(1.645*4)/0.5]²

= 13.16²

= 173.18 is approximately equal to 173

The company has to study 173 machines.

since proposition states that a number is greater than 25, if is true then the number must actually be greater than 25.

this implies that all possible options, except 24, can be accepted

72 is the answer to this problem