
Advanced Statistics Advanced Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
November 23rd, 2013, 06:25 PM  #1 
Newbie Joined: Oct 2013 Posts: 3 Thanks: 0  sample size Question#1 How many concrete cubes should a construction site Materials Engineer take in each sample (batch) if the Contract Specifications require that he should be 90% confident that his estimate of the mean concrete strength does not deviate from the true mean strength of that day’s concrete by 3 N/mm2. From past experience, it has been found that the strengths of concrete produced are normally distributed with a variance of 12.25 N/mm2. Question#2 For a normally distributed population, how many samples should we take in order to ensure that there is a 98% chance of obtaining a sample mean falling between 105 and 115? The population mean and variance are 110 and 86 respectively. 

Tags 
sample, size 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Sample size question  MM4TW  Algebra  2  December 6th, 2012 10:05 PM 
Chi Square Sample Size  Aqil  Advanced Statistics  0  March 21st, 2012 01:28 AM 
Sample Size and Std Dev  jskrzy  Algebra  1  November 16th, 2011 04:17 PM 
Sample Size  waza086  Algebra  0  March 21st, 2010 02:54 AM 
Sample Size  symmetry  Advanced Statistics  0  March 30th, 2007 04:09 PM 