How Science Works Flashcards
Why is there a control variable in an experiment?
- To provide a value to compare the results of the experiment to
- To determine that any change in the dependent variable is directly caused by the changes to the independent variable
How is a control group treated?
Treated the same/fake drug administered in the same way. Given a fake drug/saline water.
What is the independent variable?
The thing that is changed
Where are the results for the independent variable placed`?
On the x-axis
What is the dependent variable?
The thing that is measured
Where are the results for the independent variable placed`?
On the y-axis
What is the control variable?
The thing that is kept the same
Why are the percentages/rates/ratios used?
Allows comparison between results as they have different starts (e.g. starting mass/birth rates/population sizes)
How is correlation and causation explained?
1) Say if there is a negative/positive correlation
2) Even with correlation this does not mean causation
3) Could be due to another factor (give example)
4) State the points that do not fit the pattern
How is the validity of the results explained?
- What may have affected the accuracy of the results? e.g. sample size, appropriate temp/conc/time, repeats, standard deviation
- Look for results that do not fit the pattern and quote them
How do you avoid bias in an experiment?
Make sure that everything is random and avoid personal opinion in the conclusion.
How do you evaluate an experiment?
- Describe the positive and negative aspects of the experiment.
- Say what support the conclusion and what doesn’t
- Quote data
How do you describe the results of an experiment?
• Say what you see and quote figures
How do you explain the results of an experiment?
Say why something has happened in detail with key terms.
Why is the mean value used?
Allows comparison with different samples
How are unknown values found?
- Plot known variable
- Draw line of best fit
- State where you would extrapolate data from
What is the standard deviation and what can this tell us about the results of an experiment?
- Spread of the data around the mean
- If they overlap there is no real difference between the results
- If they don’t overlap then there is a real difference between the results
How is the probability of chance used to explain results?
• If there is a real significant difference there is less than 5% probability that the results are due to chance.
How is the percentage uncertainty found?
• Smallest division of measuring instrument divided by half then divided by value measured
What is mean by high precision?
Results are spread close to the mean.
What is meant by a repeatable results/experiment?
The original experimenter repeats the investigation using the same methods and equipment and gets the same results.
What is meant by reproducible results?
If the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.
When is a logarithmic scale used?
When using really big scales or ranges
How is the percentage change calculated?
(Change/orginal) x 100
What is meant by accuracy?
If the values obtained are close to the true value
How is accuracy increased?
- Carry out more tests around the estiamted value to make interval smaller
- Repeat each test
When is a t-test used?
Looking at differences between two means
How do you know if results of t-test are significant?
The probability is less than 5% that the results are due to chance
When is a spearman’s rank used?
Looking for a correlation between two sets of continuous data.
What do the spearman’s rank results state?
value of + = positive correlation
- = neagtive correlation
1 = perfect correlation 0 = no correlation
When is a chi-squared test used?
When looking at frequencies of categoric data with the same dependent variable
What are rules for scientific drawings?
- No sketching/hanging lines/shading/cross lines
- Give the scale
- Draw on the left and label on the right (with straight lines)
