# Adding 1% error to data in a column in Minitab

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#### zak9000

Hi Guys

I am new to using minitab. At the moment i am trying to do perform a simple exercise. I column with 1000 voltage values. I know that the error associated with the voltages is 1%. Now I want to create another voltage column with the voltage+-1% voltage error.

so I went to calc and attempt to create an expression. I first began with:

voltage+(1/100*voltage)

but in this case i will always have the error added. Instead i am looking for something like:

voltage+rand(1,-1)*(1/100*voltage)

the rand function will generate a random number between 1 and -1. However unfortunately this function does not exist within the minitab calculator. Do you guys know of a simple way to create this function in minitab

#### Stijloor

Staff member
Super Moderator
A Quick Bump!

Can someone help?

Thank you very much!!

#### reynald

##### Quite Involved in Discussions
Hi,
You can compress this answer in 1 long formula but I will answer step by step so that it will be easier to follow.

1. Create a column that will contain your random numbers. Then to calc-->random data-->uniform

2. Then on the other column modify your formula to have an if condition:
if( random < 0.5, voltage+(1/100*voltage), voltage-(1/100*voltage))

Note: I don't have mintiab in my laptop now so I can't verify the syntax of the formula. But somehow that is the concept.

The beauty of this approach is that you can control the % (-) and the %(+). Just change this value:
if( random < 0.5, voltage+(1/100*voltage), voltage-(1/100*voltage))

#### reynald

##### Quite Involved in Discussions
As for this:
"rand function will generate a random number between 1 and -1",
use this transformation
-1 + random*2
or in generic form
min_value + random*range