EMPA Flashcards
What are buffers used for?
Maintain constant pH
You left … in a waterbath for 5 minutes first, why?
To equilibrate
Did you use a water bath? Why?
Yes, temperature fluctuates more in air
How did you make sure the temperature was reliable?
Measure temperature at the beginning and end, to show there was little variation
Why did you do repeats?
Allows calculation of a mean
Allows anomalies to be identified
Was your data reliable? Explain your answer.
Reliable - all values similar (or points close to best fit line)
Unreliable - give anomalous data (or points not close to best fit line)
Why are control groups used?
To show the results were caused by the variable tested
It was difficult to decide the endpoint when observing colour change, how could this be improved?
Use a colorimeter, record time taken to reach a set value
Scientists found a correlation between x and y and suggested x caused y. Is this a valid conclusion?
No, correlation does not show a causal relationship
It may be due to another (named) factor
Why did you shake the test tube?
To mix the solutions/ensure something was covered
Why are were cold solutions used?
To slow down enzyme activity
Why was an isotonic solution used?
Same water potential as the cells, so prevents bursting/shrinking
How should the control group be treated?
Exactly the same as the experimental group, but not given the drug/given a placebo
… was done randomly, why?
To avoid bias
Why were a large number of … used?
To ensure the sample was representative
or
Minimise the effect of anomolies
How could you place quadrats randomly?
Random number generation (e.g. using a calculator)
Using tape measures to form a grid of coordinates
… was given as a percentage/per 1000 why?
To allow comparison between … with different sample sizes
What information does standard deviation give about the data?
The spread of the data, about the mean
What things affect the validity of conclusions?
- Animals being used, data being applied to humans
- Subjectivity of tests
- Number of species/types of … researched
- Sample size
- Overlap of data
- Suggesting a causal link from a correlation
How is the test statistic interpreted?
Our value > critical value/bars do not overlap
⇒ reject null hypothesis
⇒ < 5% probability that the results are due to chance
When investigating animals, why should the test area be cleaned between trials?
The animal may leave smell/substance/trail
Which could affect other animals
In what ways should the organisms used be similar?
Same previous treatment
Same size/age
Same species
Why did you do x number of trials?
Large enough for stastical test
The larger the sample, the more respresentative it is of the population
Not so many that insufficient time
Did you repeat the experiment using the same organism? Why?
No:
Prevents learning
Reduces stress
How can the data be used to see if there is a significant correlation/difference between x and y?
Construct null hypothesis
Use relevant statistical test to calculate the test statistic
Look up the critical value in the table (see if bars overlap for SE)
Use this to accept or reject the null hypothesis
