In article <[EMAIL PROTECTED]>, Alan McLean <[EMAIL PROTECTED]> wrote:
>In practice the population is almost always a model - at best it is ill >defined. So the value of sigma is virtually never meaningfully 'known'. >At the same time, a role of statistical analysis is to save one from >jumping to unwarranted conclusions - so one should be conservative. On >this basis, it is preferable to use t even when you might think z is >reasonable. But what if the sample standard deviation that you computed to do your t test is substantially less than what you think sigma is? Is it really "conservative" to ignore this, and quote a result that is based on what you have reason to believe is an optimistic estimate of the accuracy of the observations? Radford Neal . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
