Getting Good Results Flashcards
A good experiment is one which gives what kind of results?
Precise.
Repeatable/reproducible.
Valid.
Accurate.
Precision.
Precise results don’t vary much from the mean.
Precision is reduced by random error.
Repeatable/reproducible.
Repeatable results mean if the same person repeats the experiment using same method/equipment, they will get same results.
Reproducible means if a different person does experiment with slightly different methods/equipment the results will be the same.
Validity.
Answer original question.
To do this you need to control all variables to make sure you’re testing one thing.
Accuracy.
Accurate results are very close to true answer.
Human interpretation can reduce accuracy of results.
What 4 things should you consider when designing a good experiment?
Variables.
Controls.
Repeats.
Sample sizes.
What are variables?
Quantities that have potential to change.
eg temp or pH.
In an experiment you change one variable and measure its effect on another variable.
What is the independent variable?
The variable that I change.
What is the dependent variable?
The variable you measure.
What is the control variable?
The variable you keep constant.
Name the independent, dependent and controls in an investigation on light intensity affecting rate of photosynthesis?
Independent variable - light intensity.
Dependent variable - rate of photosynthesis.
Controls - pH, temperature, time.
What are negative controls?
They are used to check that only the independent variable is affecting the dependent variable.
They don’t effect experiment.
Example of a negative control.
When investigation how light intensity impacts rate of photosynthesis, set up a negative control in which the experiment is carried out in the dark.
No photosynthesis should happen.
What is a positive control?
They show what a positive result of the experiment should look like, to check if its possible.
Example of a positive control?
If you’re testing the presence of glucose in a solution.
Carry out Benedict’s test on a sample you know contains glucose.
This will show what a positive result should look like.
What are control groups?
A group which is treated the same way as the experimental group, apart from factor you’re investigating.
Why is doing repeats good?
Reduce random error.
Precise.
Repeatable.
Reduces the likelihood the results are due to chance.
How can you reduce chance of random error?
Take several repeats.
Calculate mean.
Why is sample size important?
Having a large sample size reduced the likelihood the results are due to chance.
If you get the same result over a large sample size it shows you have a representative sample.
What should you do when doing a study involving humans?
Make sure the other variables are the same.
Same age, sex, ….
Why is a placebo important?
So people don’t assume they have improved when they haven’t, because they think they have been treated.
How do scientists find out if a result is due to chance or not?
Statistical test.
