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o00 https://www.mathxl.com/Student/PlayerTest.aspx?testid-123899380&centerwin.yes; Britt Hun Quiz: 09 Quiz Chapter 5 (part 3) This Question: 5 pts 2013(0com plate) This The cholesterol levels of an adult can be desaribed by a normal model with a mean of 181 mgldL and a standard deviation of 30. a) Draw and label the normal model. O A O c. b) What percent of adults do you expect to have cholesterol levels over 190 mgldL Round to two decimal places as needed.) c) What percent of adulits do you expect to have cholesterol levels between 130 and 140 mg/dL Round to two decimal places as needed.) d) Estimate the interquartile range of cholesterol levels. QR.mod Click to select your answerls)

Explanation / Answer

a)

The mean is at 181, within 1 standard deviation is 151 to 211, within 2 standard deviations is 121 to 241, within 3 standard deviatons is 91 to 271.

The pictures are blurry, but I think it is letter C which has these endpoints. Please look for these endpoints. [C]

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b)

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    190      
u = mean =    181      
          
s = standard deviation =    30      
          
Thus,          
          
z = (x - u) / s =    0.3      
          
Thus, using a table/technology, the right tailed area of this is          
          
P(z >   0.3   ) =    0.382088578 = 38.21% [ANSWER]

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c)

We first get the z score for the two values. As z = (x - u) / s, then as          
x1 = lower bound =    130      
x2 = upper bound =    140      
u = mean =    181      
          
s = standard deviation =    30      
          
Thus, the two z scores are          
          
z1 = lower z score = (x1 - u)/s =    -1.7      
z2 = upper z score = (x2 - u) / s =    -1.366666667      
          
Using table/technology, the left tailed areas between these z scores is          
          
P(z < z1) =    0.044565463      
P(z < z2) =    0.085864905      
          
Thus, the area between them, by subtracting these areas, is          
          
P(z1 < z < z2) =    0.041299442 = 4.13% [ANSWER]

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d)

As

IQR = 1.3489795*sigma

Then

IQR = 40.46938501 = 40.47 [ANSWER]

      

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