B
Suppose I want to compare 2 different processes applied to a product, such as a wheel that is quenched in water after casting and a wheel that is NOT quenched after casting (we are looking at flange thickness variation). Seems like a 2 sample t-test is what I need, please correct me if I am wrong.
So the next question is, what should my sample size be?
Can I use the 2-sample t function located under the "power and sample size" in Minitab? Problem with this is that it requires me to insert the std deviation of the population (which is unknown). Unless I can insert the std deviation of a previous sample here... confused...
Is there another way to calculate what the correct sample size should be if I do not know the std deviation of the population?
So the next question is, what should my sample size be?
Can I use the 2-sample t function located under the "power and sample size" in Minitab? Problem with this is that it requires me to insert the std deviation of the population (which is unknown). Unless I can insert the std deviation of a previous sample here... confused...
Is there another way to calculate what the correct sample size should be if I do not know the std deviation of the population?