How would you design an experiment to identify the most drought-tolerant grass from four grass seed samples?
Posted by davidawesomelandscaping
What should the responding variable be? The height? Don’t different grass grow a different maximum lengths?
A sketch of a procedure would be really nice 
Thank you soooo much! You’re the best!!! 
January 23rd, 2010 at 8:31 am
the gut response is to grow all four with not much water and see which gets bigger - but you very rightly note that some grasses are just bigger naturally, nice one. that’s a scientist’s instinct that is!
what you need is a ‘control’ - a case where you don’t put your samples under experimental conditions, to see what the default state is. so you would need to grow each plant under dry conditions, and also grow another sample of each under normal conditions with adequate water. by measuring the *difference* between the normal and dry plant of each sample, rather than the absolute height, you’ll find out which is more tolerant.
in total you will have 8 plants - one of each sample in each of the two test conditions (dry vs normal) make sure you use the same amount of water on all the dry plants, and the same for all the normal ones. making sure you have controlled for ‘confounding variables’ (things influencing your plants apart from the amount of water), for example: all in the same amount of sunlight/planted at the same depth/in the same soil/pots/blahblahblahetcetcetc… this will get you uber bonus points in your write-up
it might be worth making a few brief qualitative (descriptive) observations as well as quantitative (measuring) ones - for example, which plants lose the colour in their foliage most? or go more brittle? etc. this might help to back up your measurements and conclusions (but remember - science likes the numbers best :P).
good luck!
January 30th, 2010 at 7:12 pm
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