Unpaired (independent) t-test

Hi

I have to do a statistical test for my A2 biology coursework and because I am dealing with 2 sets of data from unmatched samples, I decided to do the unpaired t-test. My teacher gave me step by step instructions on how to do this. However, I seem to get a ridiculous t-test value of 176.

I've checked it over myself lots of times and got two other friends to check it over and they got the same answer as me. However, it seems a bit ridiculous to have such a high value when everyone else in my class who did it has got low values such as 5 or 10.

I've put screenshot in the spoiler, if possible can someone check my method to see whether I've done it right or not It's really stressing me out as the coursework has to be in for Tuesday (final final deadline) and because of bank holidays there isn't a chance of me asking the teacher.



Thanks

is your data taken from a population with a normal distribution (with equal variance)?

The population were two types of bacteria (E. coli and B. subtilus) so I assume they show normal distribution as they are living organisms.

I had anomalous results which I disregarded from calculations. I've attached the raw data if that helps.

seeing that two different species are considered I suspect the equal variance condition may well not have been satisfied. But as I said above perhaps you need more data. Have the other people you have mentionned in your class doing the same experiment with the same data?

It's too late to collect more data now and if I make it up, the teacher will know as she has checked my results. Additionally I'll have to change my analysis and discussion of the results, which will be too much.

I see where you are coming from though, as the sheet my teacher gave me with instructions on how to do the unpaired t-test, said I need 6-30 sets of data and I only have five. When I asked her about that, she said it should be fine with my data.

The other people did different experiments as it is externally marked coursework. They used stuff like different mouthwashes or different types of curry But they had similar amount of data I did.

ech....you really are in a bit of sh** situation. I don't what I can suggest then. You'll just have to present those results.

I asked my teacher very very briefly as she was in rush that I got a t-test value of 176 and she said sometimes you get that. I've checked the calculation numerous times with the sheet she gave me. I don't think it's wrong and it's just the results I got from my experiment which I can't help much.

From your understanding is the calculation above correct?

yes it is correct.