
Advanced Statistics Advanced Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
August 16th, 2017, 06:20 AM  #1 
Member Joined: May 2015 From: Australia Posts: 61 Thanks: 7  Obtaining lower and upper limit Question: What are safe cholesterol levels? Measurements of cholesterol for males 20 to 29 years old are approximately Normally distributed with mean 4.6 mmol/L and standard deviation 0.93 mmol/L. In medical diagnosis, physicians often use reference limits for judging results as ‘normal’ or else requiring further investigation or treatment. These are typically the limits within which we would expect to find 95% of healthy people. Obtain the lower and upper limit for that range in the case of cholesterol for males 20 to 29 years old. According to your range, at what cholesterol levels would we suspect a health problem? My answer: 95% of values under curve lies within two standard deviations of mean. Lower limit: μ(2 x σ) =4.6 – (2 x 0.93) =2.74 mmol/L Upper limit: μ+(2× σ) 4.6 + (2 x 0.93) = 6.46 mmol/L The lower limit is 2.74 mmol/L and the upper limit is 6.46 mmol/L for the range we expect to find 95% of healthy people. According to this range, we'd suspect a health problem for cholesterol levels below 2.74 mmol/L or above 6.46 mmol/L. Is that method of solving the problem correct? Thanks in advance 
August 16th, 2017, 10:25 AM  #2 
Math Team Joined: Jul 2013 From: काठमाडौं, नेपाल Posts: 876 Thanks: 60 Math Focus: सामान्य गणित 
I get slightly different values: Lower limit: μ(2 x σ) =4.6 – (1.96 x 0.93) =2.7772 mmol/L Upper limit: μ+(2× σ) 4.6 + (1.96 x 0.93) = 6.4228 mmol/L 
August 16th, 2017, 11:11 AM  #3 
Senior Member Joined: Aug 2012 Posts: 1,709 Thanks: 458 
Ah, lim soup.

August 16th, 2017, 02:52 PM  #4 
Member Joined: May 2015 From: Australia Posts: 61 Thanks: 7 
Hi, im confused as to why you changed the 2 to 1.96. Lower limit: μ(2 x σ) =4.6 – (1.96 x 0.93) =2.7772 mmol/L 
August 16th, 2017, 08:27 PM  #5 
Member Joined: May 2015 From: Australia Posts: 61 Thanks: 7 
My solution for this question is based off of the image i just attached which basically says that 95% of values under curve lies within two standard deviations of mean. This is why I wrote 2 x 0.93 throughout the solution. I'm not sure why we should use 1.96 x 0.93? Lower limit: μ(2 x σ) =4.6 – (2 x 0.93) =2.74 mmol/L Upper limit: μ+(2× σ) 4.6 + (2 x 0.93) = 6.46 mmol/L 
August 16th, 2017, 08:57 PM  #6 
Math Team Joined: Jul 2013 From: काठमाडौं, नेपाल Posts: 876 Thanks: 60 Math Focus: सामान्य गणित 
The curve I referred suggested the value of 95% in between 1.96 to 1.96


Tags 
limit, lower, obtaining, upper 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Vector Field upper&lower limit question  zollen  Calculus  4  August 8th, 2017 06:29 AM 
upper limit = lower limit implies convergence  zylo  Calculus  13  May 31st, 2017 01:53 PM 
Upper and lower bound of A1 and A2 ( please help me out)  Ayxd77789  Real Analysis  2  December 19th, 2016 05:35 PM 
Help Me Please with Upper and Lower Sums  VikramAhuja  Calculus  2  April 25th, 2015 07:20 PM 
Lower and upper bounds  will_hunting_math  Computer Science  13  April 6th, 2013 12:14 PM 