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A level biology STATISTICS help: Student T test. Worked examples,exam questions & critical analysis
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- Опубліковано 1 бер 2020
- Learn how to and when to use the student T test statistic for A-level Biology, how to write a null hypothesis and conclusion. In this video I go through worked exam questions linked to this exam skill, focussing on what a p value is.
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Hi Ma'am, your statistics lessons were very much thorough and were so helpful that even people like me native to very far lands are getting benefited from your videos. I wish you and your amazing channel the very best of luck. Thank you, Miss.
Thank you,!!!! so glad they help
Very helpful!!! Thank you very much for taking the time to explain this. :)
You're so welcome!
At 6 minutes, I think there may be a typo when the information from one slide has been copied and pasted and not changed. It reads '[red font] Accept the null hypothesis as the calculated value if more that the critical value' and I think it should read '[red font] Accept the null hypothesis as the calculated value is less than the critical value.' It's the 'less than' part that I'm interested in. What do other people think?
Yes you are right, I noticed that too!
hi, great video. At the start you said we do not need to calculate the t value. Is that just for AQA because i thought I had to calculate it in Edexcel B. Thanks
Hello
Your spec states
Candidates may be tested on their ability to select and use:
● the Chi squared test to test the significance
of the difference between observed and
expected results
● the Student’s t-test
● the correlation coefficient
I would have thought it would be the same for all exam boards, in that you have to calculate the stats throughout the course but not in the exam as its too much time on maths. Check with your teacher though.
@@MissEstruchBiology ok thank you, my teacher says that in the exam they give us the basic formula but we may be asked to calculate it using data in a table for example.
Hi, on the last question it says that there was a significant increase in mean species richness for habitat A and B but I’m a bit confused because the value for A is negative, so would that not be a decrease?
in ocr A your required to know how to calculate it btw
Good tip 👌
do we need to know the difference between a paired and un paired t- test on the exam ? e.g. could we be asked a question on the difference between the two ?
I don't think so
Hi, what do you say when P equals a value? So for a question I’m doing now P=6? Thank you so much, your videos really help me :)
hi im not trying to be smart here but 8:06, second red line, did you mean to write the word chance instead of change?:)
hello. Ah yes. that should say chance!
Thank you!
You're welcome 😊
hi, why is 0.05 used as the cut off point for most statistical tests
Hello,
This is because to conclude there is a significant difference/correlation you have to be 95% confident (or less than 5% probability due to chance which is p=0.05)
@@MissEstruchBiology Is there anything inherently special about this 95% probability, or is it just what has been agreed on within the scientific community?
@@solomon7009 Not sure if you still care but it's to do with the chance of hypothesis tests going wrong. There are Type I errors where a test rejects the null hypothesis even though it was correct and Type II errors where The null hypothesis itself was wrong but still accepted. 5% provides a seemingly perfect balance at getting as small as possible chance of either error occurring. When you decrease the chance of a Type I error the probability of a Type II error increases and vice versa so that is why we don't use miniscule significance levels and why 5% is used most of the time.
Is it the same as the standard error test?
no,that's different (and not of the spec anymore)
If the p value is equal to the critical value is it signficant or not? With chi squared if it is equal then it is classed as significant.
if your calculated value is equal to or greater than the critical value it is significant, but only st a p value of
Great video! Please could you go through biodiversity a03 questions please
Thanks Leah!
Do you mean questions where you have to use data to come to a conclusion and evaluate, or the practical skills linked to sampling?
@@MissEstruchBiology Conclusion and Evaluate Q
Hopefully I'll have something linked to that, focusing on critical analysis, out within the fortnight.
do you need to calculate it for ocr?
I don't think so for any exam board as it would be too much maths in a bio paper
In the final question of the video, when you say that habitat C did not show a significant change but habitat A and B did, is this in relation to the student T test or are you saying this because habitat C's change in mean species richness is only +0.12, compared to A and B's habitats of -3.22 and +2.31 respectively?
This is in relation to the p value for the T test statistic.
You can only conclude a change is significant or not using a p value, not the original mean. If you are given p values, then this is what you should be using, not the mean alone.
@@MissEstruchBiology Thank you for clearing up my confusion!!