My Math Forum  

Go Back   My Math Forum > College Math Forum > Advanced Statistics

Advanced Statistics Advanced Probability and Statistics Math Forum


Reply
 
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.
Engr Faisal hbaib is offline  
 
Reply

  My Math Forum > College Math Forum > Advanced Statistics

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





Copyright © 2019 My Math Forum. All rights reserved.