genetic crosses and the chi squared test

Question 1

the chi squared test is used to ____ ___ ____ __________.
the ____ __________ is used to …

Answer 1

the chi squared test is used to test the null hypothesis.
the null hypothesis is used to examine the results of scientific investigations and is based on the assumption that there is no difference between sets of observation, any difference being due to chance alone.

Question 2

what is the chi squared test?

Answer 2

the chi squared test is a means of testing whether a deviation between the observed and the expected numbers is significant or not

Question 3

what are the criteria that need to be met for the chi squared test to be used? (4)

Answer 3

• the sample size must be relatively large, that is over 20
• the data must fall into discrete categories
• only raw counts and not percentages, rates etc can be used
• it is used to compare experimental results with theoretical ones, for example, in genetic crosses with expected Mendelian ratios

Question 4

what is the equation for chi squared?

Answer 4

see flashcard

Question 5

what do you do once you’ve obtained the chi squared value?

Answer 5

the value obtained is then read off on a chi squared distribution table to determine whether any deviation from the expected results is significant or not. to do this we need to know the number of degrees of freedom.

Question 6

what is the number of degrees of freedom?

Answer 6

the number of cases (categories) minus one

Question 7

complete a chi squared test on a coin being tossed

Answer 7

check notes to see if correct

Question 8

what is the critical value in the chi squared test?

Answer 8

in the chi squared test the critical value is p=0.05

Question 9

what happens if the chi squared value is greater than/less than the critical value?

Answer 9

CHECK