Reply to John D's Post: I found the reliability calculator very helpful. However I would be very interested in finding out how to set up the formula for the cronbach alpha in my spreadsheet

Thanks for the accept. In fact I was still researching this for you since there is no standard excel function for calculating Cronbach alpha. Excel however has a CORELL function to calculate the correlation once the data is placed in a matrix form The following article has the mathematical formula for calculating Cronbach's alpha and shows you how the CORELL function can be used to get the alpha value from the correlation table.

In the alpha spreadsheet used in the powerpoint tutorial that we were discussing, can you tell me how I deal with missing data? - do I leave a blank space, or is there a bit of programming to be done?

Ok, after looking at the formulas and playing around with the table I can say the following about blanks.

All the formulas in the attfrD30 data sheet (e.g, Average, Sum, Standard Deviation, Variance, etc.) take account of the all cells in the table irrespective of whether they have values or are blank. In other words blank cells will be taken into account as having the value of 0. So if you remove some data, the results will change.

If you want to maintain a correct result when you have blank cells, the way I would do it is to plug in 'average' arbitrary values in these blank cells. The 'average 'arbitrary' values can be calculated by determining the real average of the range excluding blank cells, then plugging in that average value in each of the blank cells.