10.5 Quantitative investigations of variation Flashcards
what is interspecific variation?
Differences between a species and another
what is intraspecific variation?
Differences between individuals within a species
what does quantitative investigations of variation involve? (3)
- collecting data from random samples
- calculating mean value and standard deviation from collected data
- interpreting values calculated
what does random sampling prevent?
sample bias
by chance it might not be representative
what ways can you prevent bias in random sampling?
- Dividing study area into a grid
- using random number generation to get coords
- larger sample size
- statistical test/ analysis of data
how does a large sample size reduces bias?
- decreases probability that chance will affect results
- decreases effect of anomalies
- more representative
when is a sample biased?
when the sample doesn’t represent the whole population
common analysis for investigating variation
- mean
- mode
- median
- standard deviation
what’s the mean?
the average value of a set of data
what’s the mode?
single value that occurs most often
what’s the median?
middle value in a set of data
what is the standard deviation?
the spread of values about the mean
how do you calculate standard deviation?
- calculate mean value
- calculate the square of the measured value minus the mean value for each value
- calculate the sum of all of the squared values
- divide the sum of by the number of values minus 1
- square root the value
how’s the mean calculated?
total sum of all values / number of values
how do you interpret the standard deviation in a graph?
the smaller the error bar, the smaller the s.d.
the greater the error bar, the greater the s.d.
