representing classification

Question 1

what is continuous variation

Answer 1

characteristics that can take any value within a range
- eg. mass, height, weight

Question 2

what is discontinuous variation

Answer 2

characteristics that can only result in certain values
- eg. distinct features, blood group

Question 3

describe the causes of variation that result in discontinuous variation

Answer 3

purely genetic

Question 4

define polygenic

Answer 4

characteristics that are controlled by number of genes
- usually show continuous variation

Question 5

define multifactorial

Answer 5

characteristic caused by many factors, can be genetic or environmental

Question 6

describe the causes of variation that result in continuous variation

Answer 6

multiple genes (polygenic) & influenced by environmental factors

Question 7

state the types of graph used to represent continuous and discontinuous variation

Answer 7

continuous: line graph
discontinuous: bar chart

Question 8

define mean

Answer 8

average value in a data set

Question 9

define mode

Answer 9

most common value in a data set

Question 10

define median

Answer 10

middle value in a data set

Question 11

state 4 characteristics of a normal distribution curve

Answer 11

• 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

Question 12

define range

Answer 12

different between largest value and smallest value

Question 13

define standard deviation

Answer 13

measure of how spread out data is

Question 14

describe the usefulness of standard deviation over range

Answer 14

ranges uses only extreme values whereas SD uses all values in data set

Question 15

state the type of graph used to show whether there is a correlation between two variables

Answer 15

scatter graph

Question 16

define correlation

Answer 16

statistical relationship between two variables

Question 17

explain why there can be correlation between two variables without there being a direct causal link.

Answer 17

there could be a missing third variable that links the two

Question 18

explain what statistical tests are used for

Answer 18

used to determine significance of data

Question 19

define null hypothesis

Answer 19

• 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

Question 20

explain what a test statistic is

Answer 20

random sample from population
- used to decide whether or not to reject the null hypothesis

Question 21

explain what a p-value is

Answer 21

probability of obtaining test results at least as extreme as the test statistic, assuming the null hypothesis is correct

Question 22

describe what the students t-test is used for

Answer 22

• 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

Question 23

describe what a spearman’s rank correlation test is used for

Answer 23

• to consider the relationship between two sets of data

Question 24

describe what a paired or unpaired t-test is used for

Answer 24

• paired - determine if significant difference between means of two codependent samples
• unpaired - determine if significant difference between means of two independent samples