Thanks a lot..

I am really thankful for your guidance…

Madiha

]]>Yes, you are on the right track. In this case the same subject is the respondent. It looks like paired t test is the way to go.

Charles ]]>

What do you mean by same subject? Can you explain? because i m confused about it..

What i understood, here same subject means taking answers of both variables from one respondent.

I collected water quality information and health information from same household….

Am i going on right track?

Madiha

]]>Date of purchase Date of repair

my study period is three years, each date of purchase and repair is different, so some of the data have either right censored (date of repair is after end of study date) or left truncated (date of purchase is less than start of study period )

Then i need to use method of moment and MLE to estimate the parameter and fitting into 3 distributions (gamma, weibull and normal), but i don’t know how to deal with the censored and truncated data when doing MOM and MLE in excel.

Thanks ]]>

Glad you like the website.

You pose a great question. Statistics is not just a mathematical discipline, but it is supposed to provide practical application to real-world problems. In general, statistical tests are reasonably robust to small departures from the assumptions. Robust means that if you are testing whether say the p-value < .05, the test really tests for this (and not that a type I error of .05 should really be .08). Also some assumptions are more sensitive than other assumptions. E.g. ANOVA requires that the data be normally distributed and the variances of all the groups be equal. The test is quite robust to violations of the first assumption. Even when the data are not so normally distributed (especially if the data is reasonably symmetric), the test gives the correct results. ANOVA is much more sensitive to violations of the second assumption, especially when the group sizes are different. If you have very different group sizes, you probably want to use a different test. But even here, if the group sizes are the same and the largest group variance is no more than 3 or 4 times the smallest group variance, then the test is likely to be quite reliable. Charles ]]>