representing classification Flashcards
what is continuous variation
characteristics that can take any value within a range
- eg. mass, height, weight
what is discontinuous variation
characteristics that can only result in certain values
- eg. distinct features, blood group
describe the causes of variation that result in discontinuous variation
purely genetic
define polygenic
characteristics that are controlled by number of genes
- usually show continuous variation
define multifactorial
characteristic caused by many factors, can be genetic or environmental
describe the causes of variation that result in continuous variation
multiple genes (polygenic) & influenced by environmental factors
state the types of graph used to represent continuous and discontinuous variation
continuous: line graph
discontinuous: bar chart
define mean
average value in a data set
define mode
most common value in a data set
define median
middle value in a data set
state 4 characteristics of a normal distribution curve
- mean, mode, median are the same
- bell shape distribution, symmetrical about mean
- 50% of values less than mean, 50% greater than mean
- most values lie close to mean value, number of individuals at extremes is low
define range
different between largest value and smallest value
define standard deviation
measure of how spread out data is
describe the usefulness of standard deviation over range
ranges uses only extreme values whereas SD uses all values in data set
state the type of graph used to show whether there is a correlation between two variables
scatter graph
define correlation
statistical relationship between two variables
explain why there can be correlation between two variables without there being a direct causal link.
there could be a missing third variable that links the two
explain what statistical tests are used for
used to determine significance of data
define null hypothesis
- prediction that there is no significant difference between specified populations
- represents “status quo belief”, such as absence of a characteristic or lack of an effect
explain what a test statistic is
random sample from population
- used to decide whether or not to reject the null hypothesis
explain what a p-value is
probability of obtaining test results at least as extreme as the test statistic, assuming the null hypothesis is correct
describe what the students t-test is used for
- to compare the means of data values of two populations
- eg - determining whether there is statistical significance between length of ivy grown in light vs in shade
describe what a spearman’s rank correlation test is used for
- to consider the relationship between two sets of data
describe what a paired or unpaired t-test is used for
- paired - determine if significant difference between means of two codependent samples
- unpaired - determine if significant difference between means of two independent samples
