Experimental design Independent measures 1 2 Im a

Experimental design

Independent measures #1 #2 I’m a farmer and I want to test two different types of cow supplement to see which one is best, supplement #1 or supplement #2 I have 60 cows. I run the experiment for 2 weeks and then record the data control 20 cows Measure weight Measure milk yield

Independent measures Each cow is only tested in one condition It’s quick easy and if the results are clear they can be easily seen. Can I be sure all three groups were equal at the start of the experiment? Was one group naturally stronger? #1 #2 control 20 cows Measure weight Measure milk yield +15% +5% -2%

Repeated measures Each cow is tested in all three conditions It’s takes longer but my data is less likely to be skewed by uneven groups. Can I be sure the order I performed the conditions hasn’t influenced the result? Would the results be the same if I reversed the conditions? Normal farm running All cows Measure weight Measure milk yield To get a baseline reading #1 All cows for 2 weeks Measure weight Measure milk yield and then #2 All cows for 2 weeks Measure weight Measure milk yield +9% +6%