1 Excel Basics & Diff Error Prop

Excel Basics

Bruce Phebus

Today We Will…

Using Basic Functions

Evaluating Functions

Designing a Work Sheet

Start Graphing

Linest

Got Questions?

We’ll Try and Have Answers

Be patient there are only two of us

Intro to Excel & Math

You can only have one = sign and it must be first!

Only () work in excel does not like other brackets!

(Excel colors them to help you tell them apart and bolds them when you move the cursor over them, yea this barely helps complain to them)

Standard Math Cont...

* Is multiplication =5*8 gives 40

+ Is Plus =5+8 gives 13

- Is Minus =5–8 gives - 3

/ Is divide =5/8 gives 0.625 ^ is power =5^8 gives 390,625

By the way Excel doesn’t like spaces

Basic Commands

=sum(A1:An)=average(A1:An)=median(A1,An)=mode(A1,An)=counta(A1,An)Note! Two Data Sets are used in the next 2 !=slope(Y1:Yn,X1:Xn)=intercept(Y1:Yn,X1:Xn)Now I want YOU! To Find the command for R2 value for a line using the help menuUsing the Help menu is supper critical!

Ok I want You to open Excel and…Start with the equation for your grade in the class Grade in Class: say in Cell C3A1..A3 grades on midterms B1 WT midtermA5 grade on final B3 WT final

C3= A1*B1+A2*B1+A3*B1+A5*B3

Example: So if you have the first line and would like Excel to calculate it you need to write it like the 2nd.

=(A/B)*E-D

Can You Set Up A SetA Set of Macro’s That Will …

It Tells You What Grade You Would Need on the Final With x1,x2,x3 as mid term grades.

Can you change it to add an arbitrary number of tests?

Start by writing the equation forward and yes you are assigning the weight of the midterms. Your professor wouldn’t come to your house to write this into Excel for you. Assume no Home Work. Then see if you can add HW!

Combining Functions

=average(data)

Would Result in the same value as:

=sum(data)/count(data)

What Does Excel Do When it Ignores a Value?

What would the result of this calculation be?

=average(A1:A9)Cells A1:A9 = 1,1,2,2,0,0, , ,ten

It would be = 1 why?

What Does Excel Do When it Ignores a Value?

How Many Data Points Were There?1,1,2,2,0,0, , ,ten

There is 6 Data Points Blank Cells & Text Mean NOTHING to Excel

(1+1+2+2+0+0) / 6 = 1Text and blank cells are ignored

completely!(when you use the right function)

PAY ATTENTION

Choosing From Multiple Functions

Standard Deviation, σ, Has multiple commands (degrees o’ freedom= n)=stdev() n-1=stdeva() n-1=stdevpa() n=stdevp() n

Which to use for small data sets?Which to use for large data sets?

Some Functions Ignore Text

These two ignore text =stdev =stdevp

These two will utilize text (for use in logic calculations) =stdevpa =stdeva

Note the “a”

Getting Data Into Excel

Excel Reads TextTry importing data ascsv (Coma Separated Variable)txt (Text (Tab Delimited/Separated)

Please Get the data set on Housing Prices and get it into Excel

Linest! Very Central To This Course!Using the housing data on the thumb drive being passed around.

I am going to finish the lecture then return to this. (one slide I promise)Then Break / Work on the Housing Data

Then like ten more slides, and work on more data! (Then the torture is over!)

After Linest…What is Left To Do Today? Can you find the Average Value of a two story

house? (find and use “sort”) The Modal Value of a House? (not using sort) Can you change the format of the cells to

report more less digits? Show Sigfigs? Set it so it shows house price in Scientific

notation Can you set up borders around cells? Can you highlight cells? Graph House Price vs.

(try everything it takes seconds)

Ok New Stuff:Differential Error

PropagationBruce Phebus

Why on Earth Do We Need This?

►This course is about both knowing how to get the answer and knowing what it means

►Differential Error Propagation- is about understanding the uncertainty in measurement and how that effects the value calculated

Definitions: They often are used to mean the same thing

but…Uncertainty –

How unsure you are in the value.You should always know this!

Error – How wrong you are with your value.You don’t often “really” know this

Review: Volume Equations:►Volume of a Cylinder

Vcylinder = πr2l

►Volume of a SphereVsphere = 4/3πr3

What if you only had the Height & Length?

OK’ So we all have:Volume of Pill is =

πr2l + 4/3πr3

in Height & Length?π(H/2)2(L-H) + 4/3π(H/2)3

H = Height of PillL = Length of Pill

The partials differential with respect to the Input values is?

►You now need to finddV/dH = ?dV/dL = ?

Because they go into:δV is =

((dV/dH)δH)^2+(dV/dL)δL)^0.5𝛿V=[(𝑑V

𝑑H𝛿H)

2

+( 𝑑V𝑑L

𝛿L)2]

12

Differential Error Analysis…δV is = ? Here is what you should

have…

dV/dH = (π/2)HL-(3/4) πH2+(1/2) πH2

dV/dL = (π/4) H2

δV is = [((dV/dH)δH)^2+((dV/dL)δL)^2]^0.5

What is the final function?

The Questions for TodayWhat is the volume of each Pill? in mm3

What is the uncertainty in that Volume?Which value is dominant in calculating the uncertainty?

δH 0.003 mmδL 0.005 mm

How would you get theabove values?

How do you get δH & δLIn Real Life?

There Are Two Primary Wayso Know the Uncertainty in Measuremento Take the standard deviation of a

population Known! to be perfect by some other meansUsing the Standard

Deviation is the poorer option but is often used incorrectly!

Why?

Answer These Questions• What was the volume difference between

the largest and smallest pill?• Compare uncertainty in volume to its volume?

Get an error in percent?• Which Uncertainty is dominant?<=Uber

Necessary

NEXT WEEK BRING A RULLERI Don’t advisePrinting one!