My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Thanks Tree1Thanks
  • 1 Post By skeeter
Reply
 
LinkBack Thread Tools Display Modes
August 27th, 2017, 06:00 AM   #1
Newbie
 
Joined: Nov 2016
From: USA

Posts: 26
Thanks: 1

TI-84 calculator VS. hand calculation: why different answers to same problem?

If you have a TI-84 model calculator, then maybe you can figure out or explain what is causing the difference in answer when solving it by hand VS. calculator.

I am finding the standard deviation of five numbers:
20, 22, 24, 26, 28

The mean of these five numbers is (120/5) = 24

Using the formula by hand, I get:

SQRT [(20-24)^2+(22-24)^2+(24-24)^2+(26-24)^2+(28-24)^2)/5]
SQRT [(16+4+0+4+16)/5]
=SQRT [40/5]
=SQRT 8
=2.83

However, using the TI-84 PLUS calculator I get the answer of 3.16.

Here is what I found online on how to calculate standard deviation on the TI-84 PLUS:

2ND LIST
Tab across to select MATH
#7 STD DEV

StdDev({20,22,24,26,28}) ENTER
Answer = 3.16

I think what the TI-84 is doing is subtracting 1 from the denominator, using 4 instead of 5.
SQRT (40/4)
=SQRT(10)
=3.16

What is going on with my calculation on the TI-84 calculator?

Last edited by Seventy7; August 27th, 2017 at 06:07 AM.
Seventy7 is offline  
 
August 27th, 2017, 07:32 AM   #2
Math Team
 
Joined: Jul 2011
From: Texas

Posts: 2,628
Thanks: 1308

The TI84 is calculating the sample standard deviation.

see explanation at this link ...

math.stackexchange.com/questions/15098/sample-standard-deviation-vs-population-standard-deviation
Thanks from Seventy7
skeeter is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
answers, calculation, calculator, hand, problem, ti84



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
A creative android calculator : Blocks Scientific Calculator CoarxFlow Math Software 5 August 26th, 2016 08:37 PM
My Graphing Calculator Gave Me Inconsistent Answers EvanJ Calculus 3 September 29th, 2015 09:48 AM
Train Your Mental Calculation by a Calculator plasticman99 Math Software 1 May 26th, 2015 03:29 AM
Linear regression with calculator or geogebra (only calculation) Zman15 Elementary Math 3 March 27th, 2015 11:52 AM
Hand shaking problem Shen Elementary Math 7 June 6th, 2014 02:59 PM





Copyright © 2017 My Math Forum. All rights reserved.