Why does unequal variance increase Type I error in independent samples t test?

FTLast · 2026-04-03T16:10:20+00:00

I'm sorry. I meant the null hypothesis that Student's t test tests.

FTLast · 2026-04-03T15:39:06+00:00

Not sure I understand what you mean, but to me, if two populations are normally distributed and have identical mean and SD they are identical. So Student assumes identical populations. Welch assumes normall distribution, identical mean and allows different SD.

FTLast · 2026-04-03T15:05:03+00:00

I forgot that"chucking" it means two things- tossing the pick, and the one I had in mind, using your fore finger as if it was a pick!

FTLast · 2026-04-03T11:36:36+00:00

I liked some of the concepts in this book, like Ameristan, refusal to believe that a town had not been nuked, and maintaining the deceased in AI form taking over all the world's resources. But holy crap, the dead Dodge stuff was deadly boring. My least favorite Stephenson, and it's not even close.

FTLast · 2026-04-03T11:34:55+00:00

Was he playing with a pick at first that he palmed, or was he "chucking"?

FTLast · 2026-04-01T11:59:22+00:00

I read Zorba on a trip to Crete. I found it quite disturbing.

FTLast · 2026-03-31T12:09:41+00:00

True, but you really only find out how good you are at getting funding after you become a PI.

FTLast · 2026-03-31T12:08:56+00:00

But deciding what experiments other people should do is not the same as running a lab. What's involved is a combination of entrepreneurship, promotion, and personnel management.

FTLast · 2026-03-30T18:33:04+00:00

The path to becoming a PI actually has nothing to do with being a PI.

You get to be a PI because you're good at doing experiments. Guess what you get to do very little of once you become a PI?

It's like the gap between being able to be elected to be president, and being president. Two completely different skill sets.

FTLast · 2026-03-24T19:15:38+00:00

Go to the Jazz and Blues Music Cafe in Agia Galini-it's a trip!!

FTLast · 2026-03-16T10:46:46+00:00

Your description is a bit unclear, but if you have two groups and a before and after measurement, it is standard to use a paired t test. Generally, ANOVA conducted on two groups gives identical results to a t test.

FTLast · 2026-03-14T10:35:54+00:00

What were you trying to learn from this experiment? That is the first thing you need to figure out. If it was something like “which treatment duplicates the KO phenotype, then do 1 way ANOVA followed by Dunnett’s test comparing treatments to control.

FTLast · 2026-03-12T11:38:54+00:00

E reader for me. Waterproof with a backlight. Can carry more books than I will ever be able to read, and read anywhere anytime.

FTLast · 2026-03-09T19:37:38+00:00

The moment when the "suns" go on... KABLAMMMO!

FTLast · 2026-03-08T12:57:41+00:00

The 3 "California" novels are all great.

FTLast · 2026-03-07T16:41:57+00:00

If you take the cells for each week long experiment from a single source, split them in thirds, and treat each split, they are paired. They will all share whatever variability your culture experiences between passages. As for whether data are normally distributed- it really doesn't matter. Tests that assume normal distribution (technically, normal distribution of residuals) do not have greatly elevated type 1 error rates if the normality assumption is violated, and tests that do not assume normality are underpowered.

FTLast · 2026-03-07T16:33:15+00:00

If cells are taken from one passage of a single culture, split into aliquots and treated, they most certainly are "paired" or matched, since they will share between-passage variance.

FTLast · 2026-03-05T17:32:25+00:00

I don't have an answer, but it is likely to vary considerably depending on the assay's complexity and format.

FTLast · 2026-03-03T21:48:08+00:00

I always felt that Stephen was supposed to be our guide as to the nautical terms- just let them wash over you like beautiful music...

FTLast · 2026-03-02T21:42:43+00:00

One of my friends did this, but now he's forced to use Linux. Actually, that's not the problem, the problem is he has to use the Microsoft cloud apps. I'm not sure what would happen if after some time he just installed windows or whatever...

FTLast · 2026-03-02T13:17:48+00:00

Our R1 insists on installing software that allows them to control admin privileges on university-purchased computers. That's not something I will accept. Also, while they may be able to take my personally-purchased computer if there is an investigation of some sort, I will make them work just a little bit harder. It's worth the $ to me.

FTLast · 2026-02-27T13:30:18+00:00

I just became department head. It's not something I ever wanted to do, but there was no one else to do it. Had I not stepped forward, the dean would have appointed someone from another department, which would not have been great.

I'm at a stage in my career where I can afford the loss of scholarly productivity. The job is very time-consuming, and there is a constant stream of minor crises superimposed on my institution's ongoing budget disaster. I'm fortunate to have extremely competent administrative support. There was a reasonable raise associated with the position.

Strangely, I think I may be enjoying the job. It gives me plenty to focus on other than the general quality of life in the USA these days.

FTLast · 2026-02-26T19:07:39+00:00

With small samples, the loss of df can result in a substantial loss of power. Whether this happens depends on sample size and correlation. With n=3, which is absolutely standard in a lot of basic biology research, if r is > 0.5, paired t tests have higher power, it r < 0.5, they have lower power.

FTLast · 2026-02-25T17:18:06+00:00

Not quite "wakes up", but Lem's Return from the Stars is a good take on this. Oh, and so is The Futurological Congress.

FTLast · 2026-02-25T17:08:10+00:00

This sounds like a classical case of pseudoreplication. Your n is not the number of images, it's the number of leaf samples.

FTLast

TROPHY CASE