practical stuff Flashcards
What is a null hypothesis?
A hypothesis that states there is no stastical significant difference between 2 variables.
What are the 3 stats tests used?
- Chi squared
- T-test
- Spearman’s rank correlation
When is the chi squared test used?
to find the differences between observed and expected data is due to chance
When is the T-test used?
looking for differences between mean values
When is spearman’s rank correlation used?
looking for associations between different
measurements.
why are straight lines drawn between points on a
graph?
when it is not possible to predict the intermediate values
what points to mention when describing a graph?
- general, overall trend
2. peak of data
why is a pen not used to draw the origin line in chromatography?
ink and pigments would mix
describe how chromatography is used to separate pigments after pigments are applied
- placed in solvent with the origin line being above the solvent
- remove before the solvent reaches the top
describe how a sample from a plot of land is selected at random
- make grid of plot
- use random generator
- to generate co-ordinates
why are logarithmic scales used?
when there is a large range of quantities
why are data loggers used?
- more accurate
- can measure to a greater no. decimal places
- Data logging can be carried out 24 hours a day, 365 days of the year.
- No need to have a person present.
- Time intervals for collecting data can be very frequent and regular
conclusion from chi-squared
if the calculated value of chi-squared is larger than the crititcal value at p=0.05,
then there is less than 5% probability that the differences between the observed and expected data are due to chance
and so the difference is significant.
Therefore, we reject the null hypothesis
suggestion when a toxic/harmful form of medication needs to be used
use small amounts
