representing variation graphically Flashcards
What is discontinuous variation?
a characteristic that can only result in certain values is said to show discontinuous variation (or discrete variation) e.g. sex - only two possible values, male or female
How is discontinuous variation usually shown graphically?
in a bar chart or pie chart
What is continuous variation?
a characteristic that can take any value within a range e.g. height
What is a continuum?
there is a graduation in values from one extreme to the other of a characteristic (a gradient)
What is the difference between how discontinuous and continuous variation is controlled?
discontinuous is controlled by a single gene continuous - number of genes (polygenes), also often influenced by environmental factors
How is continuous variation shown graphically?
frequency table -> histogram , curve is drawn
What is a normal distribution curve?
when continuous variation data are plotted onto a graph they usually result in the production of a bell-shaped curve the data is said to be normally distributed
What are the characteristics of normal distribution?
mean, mode and median are the same symmetrical about the mean 50% greater than mean most values lie close to the mean, individuals at the extreme are low
What is standard deviation?
a measure of how spread out the data is
the greater the SD the greater the spread of data
in terms of variation, a high SD means a large amount of standard deviation
What is the meaning of the letters for standard deviation?
x = each value
x(bar) = mean value
N = number of values
What is the student’s T-test?
used to compare the mean values of two sets of data
data collected must be normally distributed and enough data to collect a reliable mean
What is the meaning of the letters for the students T-test?
s = standard variation
What is correlation?
relationship between data
positive correlation - as one set of data increases in value the other also increases
negative - as one increases, the other decreases
no correlation - no relationship between data sets
What is the meaning of the letters for the Spearmans rank correlation coefficeint and what is it used for?
finding the correlation coefficient
d is the differences between the two ranks (squared)
What do the vlaues of the spearments rank correlation coefficient show
- closer to +1 or -1 the stronger the correlation
