10.6 Representing Variation Graphically Flashcards
What is discontinuous variation?
Characteristic that can only take certain values
What is discontinuous variation determined by?
Genetic factors only
Examples of discontinuous variation
Animal’s sex
Shape of bacteria
Blood group
How is discontinuous variation usually represented?
Bar chart
Pie chart
What is continuous variation?
Characteristic that can take any value within a range
What is a continuum?
Graduation in values from one extreme to another
What is continuous variation controlled by?
A number of genes (poly genes)
Influenced by environmental factors
How is continuous variation represented?
Collected in a frequency table then plotted on a histogram
What is a normal distribution curve?
When continuous variation data is plotted on a graph, it produces a bell shaped curve
Characteristics of a normal distribution
Mean, mode and median are all the same
Curve has a bell shape - symmetrical about the mean
50% of values less than the mean, 50% of values greater than the mean
Most values lie close to the mean value
What is the standard deviation?
Measure of how spread out the data is - greater standard deviation, greater spread of data
Standard deviation for normal distribution
68% of values within 1 standard deviation of the mean
95% of values within 2 standard deviations of the mean
99.7% of values within 3 standard deviations of the mean
What is the t test used for?
Used to compared the means of data values of two populations
What is spearman’s rank correlation coefficient used for?
Consider the relationship between 2 sets of data
T test formula
T = (Mean 1 - Mean 2) /root of SD1/n + SD2/n
