I am currently studying

*in the Part 2 Syllabus*

**Tuckman, Art of TSM : Drift chapter**

**.**While taking a look at the spreadsheet you have prepared, I happened to come across the formula for dw in your random simulated process for MODEL 1. The formula for the same was

` =NORM.S.INV(RAND())*SQRT($D$24) `

**.**As I understand, what this formula does is it picks a random number as probability and finds its z value. However, I do not understand the underlying logic for picking up the Probability as a Random number. Would it not be acceptable to place the formula as

` =RANDBETWEEN(-2.33,2.33)*SQRT($D$24) `

?Since all we need is a random number for standard deviations around the drift, why do we need to find a random probability and then its z value, instead of directly randomising standard deviations.

Also just to clarify, the reason we take dt as \[ \sigma\;*\;\sqrt t\; \] in the rate tree formula is because we assume dw=1 ie. Standard deviations around the mean to be 1, right ?

I apologise if the question was a bit stupid. Appreciate your answer on this.

Please find a screencapture of the spreadsheet attached below.