M
mi06rasja
Hi
I in my office we only have installed minitab into one computer whitch, as you could understand, is very annoying. Thereof I have started to make my own spreedsheet in excel with some of the most frequently used minitab function i.e. Normal probability plot, IMR, MR, Histogram, Scatter plot and capability analyzis. However, now I have som problems with ploting the bell shaped curve whitch can be found in the minitab capability analyzis. does anybody know the formula for the bell shape curve is in minitab?
My assumption was that this bell shape curve was the same as the one I found in my statistical handbook for the normal distribution but when I use this I don't get the same witdh (deviation) as when I compeare with Minitab. I have pased some of my vba code below in order to discribe my solution so far. Does anybode see what Iam doing wrong?
The code in my macro is buildt in a way that the program starts at Xbarbar and checks wether or not (the y value in the bell curve) I am below a certain number, in my case 0,001. The program then goes backward until Iam below that number and counts every loop. I then double the value for the loop counter and use that counter in order to start writing each value. Later on i make a diagram using this data.
In my head it should work fine but the curve doen't look the same as in Minitab.
The value of x in that formula does that have any connection to the samples i have gathered or is it, as I think it is, just ranged values near the Xbarbar?
c8 = (Application.Max(Sheets("Measurements").Range("B3:B" & RowCount)) - Application.Min(Sheets("Measurements").Range("B3:B" & RowCount))) / (RowCount * 100)
x = Xbarbar
c10 = 1
Do Until (1 / (StdDev_within * (2 * Pi) ^ 0.5)) * Exp(-((x - c8 * c10) - Xbarbar) ^ 2 / 2 * StdDev_within ^ 2) < 0.001
c10 = c10 + 1
Loop
x = x - c8 * c10
c9 = 0
For c11 = 1 To c10 * 2
Sheets("Data").Cells(c9 + 15, 14) = (1 / (StdDev_overal * (2 * Pi) ^ 0.5)) * Exp(-(x - Xbarbar) ^ 2 / 2 * StdDev_overal ^ 2)
Sheets("Data").Cells(c9 + 15, 15) = x
c9 = c9 + 1
x = x + c8
Next c11
I in my office we only have installed minitab into one computer whitch, as you could understand, is very annoying. Thereof I have started to make my own spreedsheet in excel with some of the most frequently used minitab function i.e. Normal probability plot, IMR, MR, Histogram, Scatter plot and capability analyzis. However, now I have som problems with ploting the bell shaped curve whitch can be found in the minitab capability analyzis. does anybody know the formula for the bell shape curve is in minitab?
My assumption was that this bell shape curve was the same as the one I found in my statistical handbook for the normal distribution but when I use this I don't get the same witdh (deviation) as when I compeare with Minitab. I have pased some of my vba code below in order to discribe my solution so far. Does anybode see what Iam doing wrong?
The code in my macro is buildt in a way that the program starts at Xbarbar and checks wether or not (the y value in the bell curve) I am below a certain number, in my case 0,001. The program then goes backward until Iam below that number and counts every loop. I then double the value for the loop counter and use that counter in order to start writing each value. Later on i make a diagram using this data.
In my head it should work fine but the curve doen't look the same as in Minitab.
The value of x in that formula does that have any connection to the samples i have gathered or is it, as I think it is, just ranged values near the Xbarbar?
c8 = (Application.Max(Sheets("Measurements").Range("B3:B" & RowCount)) - Application.Min(Sheets("Measurements").Range("B3:B" & RowCount))) / (RowCount * 100)
x = Xbarbar
c10 = 1
Do Until (1 / (StdDev_within * (2 * Pi) ^ 0.5)) * Exp(-((x - c8 * c10) - Xbarbar) ^ 2 / 2 * StdDev_within ^ 2) < 0.001
c10 = c10 + 1
Loop
x = x - c8 * c10
c9 = 0
For c11 = 1 To c10 * 2
Sheets("Data").Cells(c9 + 15, 14) = (1 / (StdDev_overal * (2 * Pi) ^ 0.5)) * Exp(-(x - Xbarbar) ^ 2 / 2 * StdDev_overal ^ 2)
Sheets("Data").Cells(c9 + 15, 15) = x
c9 = c9 + 1
x = x + c8
Next c11