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.

w = 25

x = 155

y = 155

z = 155

further explanation is given above in the picture

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