Chi-Squared Test

Question 1

when is the chi-squared test used

Answer 1

stats test used to see if the results of an experiment support a theory

Question 2

what are the 2 results in chi-squared

Answer 2

expected: found via the theory [e.g. the phenotypic ratio once you have carried out a genetic cross]
observed: the actual results you get after an experiment

Question 3

what is the null hypothesis of a chi squared test

Answer 3

Ho: there is no significant difference between the observed and expected results

Question 4

what is the overall formula of the chi-squared test

Answer 4

X2 = the sum of (observed-expected squared, all over expected)

Question 5

how do you work out chi-squared

Answer 5

• subtract your observed from expected
• square each
• divide by the expected
• and add all up
• easy on a table format

Question 6

what is the probability you are using in chi squared

Answer 6

5%, so always only 0.05 level of probability that the difference between the results is due to chance

Question 7

what are the degrees of freedom in chi-squared

Answer 7

n-1

Question 8

what happens when your chi-squared value is greater than the critical value

Answer 8

• there is a significant difference between observed and expected
• null hypothesis can be rejected

Question 9

what happens when your chi-squared value is less than your critical value

Answer 9

• there is no significant difference between observed and expected results
• fail to reject null hypothesis