standard error???

[Happydadtoo]

Yes - you need one more graph - the rest are of dubious value - just plot sugar v gas evolved, with error bars.

You seem determined to make life as complex and difficult as possible - it's really, really easy and the simpler you make it, the more likely you are both to get the WRITTEN explanation PERFECTLY correct and get full marks.
There are NO marks for doing complex experiments, nor for advanced stats.

HD2

[fuzzyduck]

Thanks for the help!

The problem im having is i counted the gas bubbles that went through a trap attached to a bung for two minutes at cartain intervals. I checked each sugar at 6 different intervals and i had 5 sugars. I did three repeats of each sugar and have taken the mean for each time interval. I have plotted a line graph with these mean values. Should i do one line graph with all of the sugars mean values (have my y axis as time and the x as the bubbles produced in two minutes) , plot error bars and if they overlap on the graph then there is a sig. difference?

I hope that makes sense!! Thanks for the help so far.

[Happydadtoo]

First, I would calculate the mean RATE of bubbling (if you have 2 min counts, that simply means div by 2) for each sugar.

The graph you are suggesting is MAD!!!

Y axis would be rate (as above)
X asis would be time intervals
BUT, BUT BUT I can see no point whatever in doing that!!

To repeat 00's of earlier posts, there are TWO factors here - getting into the cell and turning the sugar into a respiratory component.
From then on, all is the same, no matter what

Now, the longer you let the whole thing run, the longer the cell has to synthesise the necessary proteins to speed up BOTH rate-limiting steps.
In short, it will go faster and faster
BUT
As the expt goes on, the substrate is used up
thus, as time goes on, it goes slower and slower

TWO opposing events.
ONE outcome
TWO explanations thus needed, thus attempting to explain why the methodology is fundamentally flawed (you need to ensure a constant, XS [substrate]; not possible in a school system.

Bya ll means witter on about the changes in the no of bubbles over time (it won't cost you marks) BUT, BUT BUT
The ONE thing you are attempting to show is a difference between the sugars which requires a bar chart with standard error bars.

Assuming your 6 time intervals were (basically) continuous (ie over about 30-90 mins in all), siply calculate the mean of the whole lot (= 18 readings?) turn into a mean RATE and then plot as above.
HD2

[fuzzyduck]

okay thank you very very much

[fuzzyduck]

Ahhh i think it just sunk in!!

Thats much better!

All im wondering now is how you work out the standard error. if i worked out the standard error for each of my times, do i just do a mean of that value!?

thanks very much

[Happydadtoo]

The standard error is for ALL results for ONE sugar (then repeat for each sugar)
5 sugars = 5 standard errors

take the MEAN RATE for each time for each sugar, add them all together (3 repeats, 6 times so calculate 6 means first, THEN calculate ONE standard error for the whole b****y lot and repeat for each sugar
ONE bar chart
ONE standard error for each sugar
Done
Dusted
Finished
Finito
Ended
The END!

[fuzzyduck]

THANK YOU!!!!

[Happydadtoo]

Yippee!!