Wks 03, Chapters 3
_____________,_______________,_________
Surname(e.g. Straayer),
Given Name(e.g. Dave), class mtg. time
In this worksheet we will calculate the standard deviation of the THU data we gathered the other day.
First, let’s add up all the thumb data: 2nd /STAT(LIST) / MATH / 5: sum( will put “sum(“ on the home screen of your
calculator. Now you need to tell “sum” which list you want to sum up. 2nd /STAT(LIST) / NAMES /… and select your THU
list. When you have it selected and press ENTER, it will copy the list name into the “sum(“ function. The Society for
Prevention of Cruelty to Microprocessors suggests that you close the parentheses, and press enter.
The sum of your THU list is : _____________________ Let’s store that number so we don’t have to re-key it in:
STO>/ALPHA/ LN (S) to store it in the memory named “S”.
Too get the average; we need to count the number of thumbs in our list. Two ways to do this:
1. Use STAT/ EDIT and use the up arrow to get to the bottom of the list quickly, and note its row number.
2. Try this also: 2nd STAT(LIST) / OPS / 3:dim(THU). That will show you the count.
ALPHA S / (“The count” ) STO>M will put the average in M.
Now we need to calculate a list of deviances. THU – M STO> L1 will do all the subtractions, and put the resulting
differences in L1.
Now we need to square them all. L12 STO> L2 will square all the differences and store the result in L2.
Calculate and record sum(L2): __________________
Divide that by “(dim(L2)-1). Don’t forget the parentheses, otherwise you will divide by n and then subtract one from the
resulting quotient.
What you see on your calculator now is the variance. Record it: ______________________
The final step in calculating the standard deviation is to take the square root of the variance. For this, it’s handy to use
the ANS. You just type in 2nd / X2() to get the square root function on the home screen, then type 2nd/(-)(ANS) to put
ANS in to the square root function. Don’t forget to close the “)”! Standard deviation: ______________
Now that you’ve done this, do STAT / CALC / 1-Var Stats THU, and find x-bar and Sx. Scroll to the 2nd screen and record:
X-bar: ________________
Sx: ______________
Min: _______ Q1: _________ Median: __________ Q3: ____________ Max: ________